I checked my 1 week old seedlings today and a couple of them have a purple hue on the underside of their leaves. I think its because its been cold (64-73 degrees), but i am not 100% sure whether it was caused by colder temperature or genetics. They are currently under a 600w MH and recieves 24 hours of light. pH 5.5-5.6 ppm= 50 @442. Growing in aeroponics/rockwool/hydroton. please let me know what you think, they are not stunted or anything, its just weird to see purple leaves, and i am wondering what could have caused it. should i raise the temperature in my grow room?