Post the Sears 917.xxxxxx and maybe there's a schematic available for it. Sears has "some" for the older tractors. That way one can possibly determine how your lighting system is arranged. Some are basically 12V from the battery, while others have an AC "lighting" circuit to the alternator.

I had a similar issue with the snow thrower on my Cub, but for me it was partially a brightness issue (corrected by replacing the bulbs with LED's), and partially a placement issue - the snow thrower is almost as high as the headlights. Realizing that the issue is similar to snow plows, here's what I did... I picked-up a couple auxiliary LED lights off eBay. I tried one about the size of a thumb, that had a single LED. It was OK, but I also tried one that's about 2.5" square, with 3 LED's, that throws a little wider beam. Using a couple simple "L" brackets, I mounted these using existing hood hinge screws. This placed the lights about 6" higher, and a few inches further from center, than the existing lights I wired-in a quick-connect to the original lights, so I could unplug those and plug these-in - just like a snow plow. These pull a little more current than the stock bulbs, but I don't use it that often at night, and have the tractor on a battery tender when not in use, so I really don't worry about the extra draw. I have about $15 in supplies, and maybe a hour's time in modifications. It maybe adds 5 minutes to the mower-to-snow change-over, but really helps on those darker winter nights.

Not sure what you have back filled the hole with but where pH of the soil is too high or too low, there is a lock up of nutrients (and micro-nutrients) in the soil. Google "the influence of Soil pH on Nutrient Availability". For the most part soil in Southern California is Alkaline (above 7 pH). This means that Iron and Manganese are somewhat locked (restricted). Iron is critical and is involved when a plant produces chlorophyll, which gives the plant oxygen as well as its healthy green color. This is why plants with an iron deficiency, or chlorosis, show a sickly color to their leaves. You probably need to lower the pH of the soil to around 6.5, add iron, and add a foliar application. A foliar application will assure a rapid response and prevent growth from being restricted. Most potting soils will be neutral and most people will have a problem with Iron and Manganese at some point. Iron chelate can be added as a soil drench. Apply a foliar spray. That will remedy the situation. To fix the situation you need to make the soil more pH towards 6.5. This can be done with some fertilizers, agricultural sulphur or aluminum sulphate.

I believe that you are seeing signs of blotch leaf miners....the middle image clearly illustrates their unique damage. Remove affected leaves and dispose. If you read a bit about the culture of basil, you will learn that it is a sun loving plant, full sun outside. Introduce it slowly into a more favorable location, cut it back, and pot it up into a larger container.....or in the ground.