Need a little advice

Alright guys I gotta problem with my first grow. The leaves from the bottom up to the middle of my plant are getting a little wrinkly and drooping. Now I think this could either be a humidity problem or from tempeture. My plants a week into flower and it get a little cold at night. I also don't have any humidity appliances for my grow box. Any ideas or solutions?

well hows the ventilation? does the plant have access to fresh air? intake/outtake? lights?

can i get a pic? around week 2 you would start to see the older lower leaves start to turn yellow and fall off that normal so it may just be the start of this but could be from the cold or high ph but its tuff to tell if i can't see it.