17 day old pics vanilla kush leaf problems !

Hello everyone , this is my first grow and I'm 17 days into veg under a 600 mh but dimmed to 400 watt due to heat issues ! I'm doing dwc and everything was going great to I started seeing the leaves kinda cupping up and a few little yellow spots , I'm wondering what's causing the curling up of the leaves ?? My water temp is 70 and my room temp stays between 75-82 I had my light at 600 watt and 12 inches from plants but I thought I might be to close so now I'm about 18 inches away and 400 watt . My ppm is at 340 and when I feed yesterday it was at 360 , ph 6.4 I know that's high but I correct it to 6.0 and 2 hours later 6.4 don't really know why that keeps happening any ideas ? I'm not sure how good the pics turned out I hope everything is ok .

This happens to me sometimes with my cheese strain either because of wind damage or cold temps when light off.
IMO
Hope that helps

Cupping leaf margins are usually caused my excessive heat. Your room temp might be sufficient but the temp at the canopy could still be a problem if for example your light is too close.

Thanks guys for responding so quick I hope that dimming my light and moving it up a bit will help then ! I also moved my fan away from them a bit just in case it was wind burn . Any thoughts on the ph problem ?