The most likely explanation damp-off from being too long under the humidity dome. And yes it can easily affect some and not others. This is a common problem often discussed over on the Growing from Seed forum here. As soon as the first few seedlings begin to break the soil surface and you see a hint of green stem showing the lid needs to come off or at the very least propped open. If you wait for all or even most of them to come up or for most of them to be standing upright then it is too late. Once the first few show, the rest will follow even without the dome on. Keep in mind that humidity domes are not required for germination. They are just a "tool" and they often create more problems so many don't use them at all. So no you definitely didn't want them under longer. A set of T8 bulbs puts our minimal heat and the light intensity isn't too much for them so no the light wasn't the problem. The next most likely cause is over-watering and root rot of some of the plants and yes, it too can affect some but not all. Hope this helps. Dave

Beachplant, Here In The Florida heat that grows And perform very well for me are the Following. Angel's moonlight will Bloom constantly In the heat. I Have not seen a single day on angel's moonlight with out Blooms.This Is one Brug that do not wilt in the Heat. Also new Orleans Lady will be a good one as well. Doosie is another one that will perform In the heat and does not wilt. Pink perfection is another double that Blooms And Blooms very well all summer. Pink Smitty performs well. These are just a few that I Have had a Chance to evaluate this Summer and They have earn a permanent Spot in My Garden. HoneyBunny/Barbra, You Should see your Red zinger Hibiscus You Sent Me This Summer. It Now Stands Around 4 feet And It Is a Vigorous grower as well. Chocolate Brug

Each bulb is supposed to be 20W at 720 lumens is this enough for growing my seedlings. Also i bought GE Plant bulbs so i dont know if it is supposed to be less bright than normal?

Yeah. Maybe leverage isn't the right word. If you pulled on the far one, it would hit the center bar, so it wouldn't come off. But the close one doesn't have anything to hit. Well, there is that little lip, but I guess it depends on how hard you tug. ;-) I don't have one of course, so I don't know that would happen, but that's the only possible problem I could think of. I wanted to get the one sided kind for my DS who won't put on a roll, so I was looking these up a few weeks ago. I remember someone mentioning that you needed to hang it where you would pull against the attached side. If I had time I'd try to locate the thread. I did buy the one sided one, but it's not up yet, so no feedback...