Curling upwards on one side

Hello. What does a curling leaf indicate? Its curling upwards on the side. Also, on the very tips of the leafs they are brown and dead. I have them at about 85/87F when the lights are on and im aware that its a little to hot but I cant afford to fork out more money on a top notch clling system. They are under a 400W HPS light at about 2 feet. I water them about 1/2 days, basically I stick my finger in the soil and see if its moist or not to check. Dont give them nutes at the moment as I thought I had to nute them when they enter flowering? The plants are new, about 3 weeks old, looking healthy other then the above mentioned. Any tips/advice would be wicked. Thanks!

if you cant fix the heat issue its going to cause you problems though out your entire grow, i would concentrate on getting that fixed before anything else. even just a box fan hung near the top of the door will help remove some of the heat.