Watering? Wrinkled leaves?

I am on my first grow but have a lot of help from a friend who is an expert. Have a nice t5 8 bulb set up in a large 200 cf + room. Temps 65-78 (perfect) and humidity staying at around 40-45%. All of the girls are doin good except for my largest purple kush. It hasnt perked up in a couple days. The leaves also have a little wrinkle to em but i think its from letting it get too dry one day. Any suggestions? How should i water? I thought i was gettin the hang of it until it started to droop and hasnt sprung back up. I am starting my new light cycle today as well(12/12). Any tips? PEACE

Could be a few things man,try flushing it,then use a mild solution when feeding,could be just a bit stressd after the drought,