I am flowering now with Mars hydro LED and a generic LED panel, I added some t-5 high output desert UVB lamps, 22 inches, two of them. I had them about 14 inches from plants during the 12 hour light on period. It started to fry them so I turned it off, flushed and added fresh water. They all recovered except 1. My question is do you use UVB during flowering to induce high crystal/trichome production. If so how far away from plant tops and how many hours in a day with lights on? Also I had several old 48 inch t-12 flourescent tubes and put them about 6 inches away from sides of plants )replaced bulbs with 6,500 Kelvin. They started to get wilty, how far should they be from sides?
UVB's are great for increasing thc but they're also capable of damaging the hell out of your plants if on too long which is what I think you're seeing. I'd cut the uv lights off after maybe 3-4 hours of the light on cycle, sounds like you have plenty of other lighting without it. As far as distance away from the lights, put your hand up at the canopy level, if it's too hot for you, it's too hot for your plants and you need to increase the distance until they're in proper temperature range.