Tops Of Plants Are Dry And Doing Bad Need Help

I am growing ten plants under 1000 watt light and I am using advanced nutients. Everything was going great untill about two weeks ago. The tops of my plants startedto turn yellow and dry and brittle not all the plants are doing it but most are. I went and bought AN revive and it has not seemed to do anything yet. Does anyone know if this is a diffecency I thought it could be silver. The other day a spotted a couple fly like creatures and Mabey the brittle tops are from them. Also it seems as if the problem is only coming from the top down mabey a few inches. Again the tops seem to be dried up almost like the light burnt them but us not possible because the light is not that close to them. Also I am using a room ac and I am wondering if the problem is from that. Someone please help if u can thanks

how far away are your lights? Any photos?

What kind of medium r u using? If it looks burt but couldn't be light then it u may be overdoing it with the nutes. What are you using for your dosage, dont use full amount recommended on back that will most lickley burn your plants up. If it is yellowing around the edges of the leaves and the leaves are curling up kind of like a taco on the sides ( kind of looks dired out.... or burned ) it could be magnisium deficiancy. let me know if this helps or give me some more info or some pics and i got u . peace !!