New grower here. 2 of my 3 LR2 plants started having this problem about a week ago. It's gotten worse, I tried correcting it initially with some nutrients. I gave them their first two feedings of 1/4 strength flowering nutrients (Technaflora Recipe For Success) but it didn't seem to help. They're on day 39 in 2 gal pots with FFOF. 250w HPS is about 4 inches from the tallest plant, it can't be heat stress. The tent is at 70F-72F with good ventilation and circulation and I can only feel slight warmth when I hold my hand by the top of the plants. Humidity is at about 42-44. It started at the tops but it seems to be working its way down, only the top leaves are doing this though. Thanks ahead of time for any help or advice.