cold night temp delima.

Growing white skunk and blueberry bliss auto. Using a local soil called Potters Gold. Under 400w MH. 3-4 day water cycle. Now the issue. I have the upper fan leaf stems turning a purple/red. My temps have been running 79° day and 64° night. My RH is around 45. I am thinking that my night temps are to low and causing the discoloration. I have a small space heater in the room to help comtrol but when it is in use it drives my RH down to 18. Which should I be more concerned about? The low RH at night or low night temps. Any suggestions would be appreciated. Can post pics if needed.

you should be fine with those temps, but I would use the heater, I don't worry about having too low a RH ,ever, too high a RH makes me start worrying about mold and fungus. those may be strains that the stems on the fan leafs turn red or purple as they mature, most of my plants do that naturally, so don't panick, your temps should be okay, but warmer will encourage faster growth.

I wouldn't worry about either personally. The night time temp going down to 64 is not perfect, but it's really OK (outdoor plants tolerate a lot colder) If your soil temp drops below 62, then you are going to slow down growth a lot though. A seedling mat under your pots will solve that, plus be cheaper to run than a space heater. RH being too low is not that bad either. Being too high is another matter altogether, then you are looking at molds, rot, bad shit. The leaf stems color is probably strain related, usually, and could be temp related, but I doubt it at those temps.

Very good. I don't seem to be having any slow growth but I have nothing to compare with.

Most people are jealous of a climate that bring the purple out. My temps are the exact same as yours during the winter.

I also have cold night temps.. around 58-60 degrees. Im growing several varieties in the tent, mostly hybrids, but the ones that really show the purple(lack of chlorophyll) are the Durban Poisons. You can tell its not a genetic purple, but a response to the cold.. interveinal purpling. I guess African races have issues with the Colorado winters

im running 68-70 lights on, 53-54 at night. its cold here and I don't want to run a heater. needless to say I have some purple plants

I tried something new with colder day and night temps on my last grow. I noticed with a couple of the same strains I grew last that they were so much frostier than the higher day and night temps, and noticed a small drop in yield. Its my moms medicine so less is better in my opinion so the slight drop in yield didn't matter.

you can get away with a lot, environmentally speaking, during veg, but not so much in flower. too low of a r/h in flower, will get you light, airy buds. they look fine, but after the cure, the weight just isn't there...