Edges Turning up

I've got a pretty good crop growing (see pic.) but with a couple plants showing some leaves turning up at the edges. They're a month old now and I recently fixed a View attachment 1307314nute problem curring a pale color that some showed. They're green and growing well now but just in the last 12 hours I've noticed the edges of leaves curling up on a couple plants. I'd like to nip this problem in the bud soon so it doesn't get worse. Any help? Too much nutes, too close to light (1000w HPS about 15-20 inches away) or something else?

Is the hps in an air cooled hood? It might be heat stress, hold your hand up to the glass. If it's too hot for your hand it's too hot for your plants.

Yeah,..I just have one of those fans in the background pointed towards it. I've put my hand near the top of the plant and it seems ok. Feels like a mid summer sun would feel like. But the one plant that is closest to the lamp is the one I'm watching so it still might be a bit too warm. I raised the lights a couple more inches. I'll see what happens.

it is heat stress 15-20 inchs is too close for a plant, 2 feet is the limit usually anything closer can cause heat stress or burning of the leaves

HAPPY GROWING MAN