I had the same thing recently happen (soil grow though). To close to the light, with humidity dome bleaches the tops. Backed the light off and removed the dome and all is well now.
You are totally correct you grumpy stoner dwarf! Keep the light far away and no humidome. I had probs with my rubbermaid level controlled bubblers for about 2-3 months (this was a long time ago) before I figured out the the humidome wasn't necessary. I cannot say exactly what will work for you, but I will tell you what I have seen work quite well. Keep your water at 74-78f, vigorously aerated but not too much because you will just get a lot of turbulence at the water surface and not enough bubbles. For most folks who use aquarium style air stones and air pumps, stirring too vigorously usually isn't even possible. If you use a Danner pond air pump (there are many sizes to choose from depending on how many bubblers you have) with an 8" round aluminum oxide air stone ( this is hard to find, but you can order it from drsfostersmith.com in the pond aeration links, I think it's on back order until next week) I guarantee that you will wonder why you ever used anything else to make bubbles. in fact, aluminum oxide air stones do not deteriorate and are the gold standard for fish farm aeration.
As for the light, I'll give you an example. If you had a 20 gallon rubbermaid brute pail 3-1/2 feet away from an adjust a wing medium sized reflector fitted with a feliz brand 125 watt 6500k compact flourescent bulb, and let's say you threw out the pail lid and used 3/4" polyshield mylarized foam board for a lid, you would be able to fit 59 clones ( with spacing of about 2-1/4" between each). They would all be happy, and wouldn't yellow prematurely. In fact, you could arrange 3 of these identical rubbermaid rigs in a triangular position under that one light fixture and they would all be happy until they are rooted. Remember the temps need to be high (74-78f) because they need some help to make roots. I've tried this set-up at 68-71 and it slows everything down 2-3 fold. Just put some superthrive at 1 drop per gallon if your tap water isn't hard ( if it only measures up to 120 ppm and naturally adjusts to the 7-7.5 range when left alone in a standing 1/2 gallon pitcher.
If you have this kind of tap water you must never add ph adjusters if you want happy expedited rooting. Oh no, I've said too much.
