i have some thoughts. I think that water spilled on your leaf and the light burned it. Some suggestions for you would be to get some plastic saucers and put under your plants so that you can water more thoroughly. You need the whole pot watered. It will make the roots go searching.. Then let the plant drink up any excess in 20 min. If there is standing water, dump it. Then go ahead with the wet/dry cycle.
Also, i hope you have a fan blowing across your canopy as well. One more thing, is get those small ones up on something, I use overturned cooking pots. You want an even canopy.