I grow a ton of Calatheas and Marantas but mine have an advantage of being planted in the ground. They just do not make good long term houseplants. There are probably several factors affecting your plant, and when they affect it "all at once", it can lead to big problems. #1--most Calathea are not high light plants. This is a good rule of thumb to follow for light: if a plant has leaves that have red or maroon undersides, its a shade or low light plant. The red coloration is a genetic adaptation of rainforest plants that thrive in moderate to deep shade. The pigment is made up of specialized cells adapted to catching what is called "green light"...this is light that filters through the canopy layer, hits the ground and bounces back up. These plants with red undersides are specifically adapted to catching and utilizing green light. So putting your plant right in an unobstructed South facing window might have been a little too much light all at once. #2--almost all the Maranta and most of the Calathea have a sensitivity to not only chlorine but also mainly to fluoride in the water. Since most municipal water supplies are both chlorinated and have added fluoride for the kids teeth, you shouldn't use it for plants like these. Your water may also contain added ammonia, which forms what are called "chloramines" which are also bad for plants. All this will cause leaf troubles like the crispy edge. Using pure spring water, distilled or purified water is a good start. #3--Humidity is a key factor for these plants and misting and a pebble tray may still be inadequate, especially in a home in a Northern zone when it gets to be winter and you turn the heat on. Air conditioning is bad enough in summer, drying out the air but the heater is killer in winter. If you can stand it, you might have better results if you purchased a cheepo cool mist vaporizer from Walmart and ran it on a timer to cycle on and off in the close proximity of any plants you have that require higher humidity. You could group all your needy plants together maybe and hit them all at once. #4--5 fertilizer sticks is just way too much for a houseplant that is already stressed.And Calathea and Maranta can be resentful of too much fertilizer. Since you have trouble keeping your plant adequately watered in the first place, it would be much better to err on the side of underfertilizing and just use some 1/4 to 1/2 strength water soluble maybe once a month. #5--if you had white bugs AND webs, you probably had a mixed infestation of mealies and mites. The webs are from the mites, mealies don't build webs. But mealies do infest the soil and also lay eggs in the soil. Calathea and Maranta are rhizomatous plants, and mealies can attack the plant below the soil level. To be certain they are gone you may need to use a systemic pesticide that goes into the soil, like Bayer, on a regular basis. Your plant sounds like it is trying valiantly to make a comeback and you sound like you did your research pretty well. Just give it time.

Well, it's impossible to totally exclude it without growing it hydroponically or in a soiless medium in an enclosed greenhouse environment since it's in the air as F2 and part of many mineral soil parent materials (feldspar, mica, etc) contain F. The soil F is mostly excluded in the roots of plants, though...not much makes it into the plant leaves/flowers/fruits. The exclusion of it in roots can effect the uptake of other nutrients via competition for uptake sites...especially Mg, Ca, Fe. In the air, F is highly soluble and it will also make it's way into the soil. You can lessen additional inputs by selectively choosing source inputs for water and certain fertilizers. Areas with excessive F (quite rare outside of industry polluted areas) can be remediated by additional Ca in the soil to help bind it up as CaF2 which is mostly plant unavailable. Long story short...you can't do much aside from managing your water sources and nutrient additions while not growing in a soil that has high parent materials that contain natural F.

Are the publications you've been reading based on some kind of scientific evidence? Granted there could always be something we don't know yet about fluoridated water but everything I've learned as a public health professional is that it is one of the single most effective public health measures ever put in place with no scientific evidence of any harmful effects. As a result there is now a generation of adults who grew up with fluoridated water who have never experienced tooth decay. I would be very interested to know if there is some new scientific evidence that it's harmful.

The problem with iron-laden water in a softener is that softener resin has a great affinity for iron and does not release it easily. Iron will slowly foul the softener resin from the inside out. Extra measures need to be taken to remove the iron. For this you have several option. The easiest option may be to simply use Iron-Remover salt. Alternatively, you can use Super Iron Out. You may choose to layer this in with your salt. If you choose this option, use 1/4 C per 40 lb bag of salt. Super Iron Out is a bit more effective if used monthly with the following procedure: Ensure you have a strong brine in your brine tank - at least 24 hours since the last regen. Dissolve 1 C Iron Out in cool water and pour it into the brine well inside your brine tank. If you don't have a brine well, for some reason, pour it down the side of the tank rather than through the salt. Place your softener into manual regen and stay right there. When backwash is complete, the softener will move to the brine/slow rinse mode. Pay attention to the way it sounds. After 10 minutes or so the sound will change when there is no more brine to draw. At this point, we want the Iron Out to sit in the softener for an hour. To do that, push the button to advance to the next regen step, then the next until your softener is back in service mode. Do this as quickly as you can. Switch your valves so your softener is bypassed and wait one hour minimum. Place your valves back in service mode and manually start a softener regen. Once the regen is complete you're good to go for another month. A liquid iron removal system such as Res Up can be installed in your brine tank to feed citric acid to the brine to aid with iron removal. My preferred methods are A or D because they employ citric acid, which is a much safer chemical than those in Super Iron Out (sodium hydrosulfite and sodium metabisulfite). The choice is yours - pick a method and follow it religiously and your softener will give you many years of reliable service.