Can't figure this one out!

Hey can anyone help me w/ this? Switched to flower 10 days ago, noticed this about 5 days ago. I read a bunch of posts, but I can't come to a conclusion. The only things I can think of is that the temps did go up to 83 degress one day, or that my night humidity is about 70%, but I'm working on that (it has always been that high, never had a problem before though).

Strain: DP blueberry
Light: 2 1000watt hps
Temps: usually about 76-78
System: ebb & flow, pots w/ hydroton & rockwool
Feed: Lucas formula, 3x/day, 1/4 strength Koolbloom

Thanks a bunch!

could be over watering

No cal/mag, do you think I need it?. Just Lucas formula w/ koolbloom. I thought it might be overwatering also, but I have kept the schedule exactly the same as my last grows and had no problems. i was thinking heat burn so I moved my lights, hope that works!
Thanks!!

I think yor right about the heat....If anything like that ever happens to me I always check pH, ppm, watering schedule (make sure timers are working} and heat issues. That will solve a majority of the problems.

Thanks everyone!

I'll second the Calmag and a good flush if you havent done so in a while