Leaves curling inwards on all plants

Hello everyone.

Well, I hope somebody will be able to help me.
First, my specs: Growing in middle-sized room, mostly passive air circulation, humidity levels +-30% (higher at night), air temperature at day 31C (can't get it any smaller), about 25 at night. I have two growboxes in there (1 mine (1,25m x 1,25m x 2m) and 1 friend's (1m x 1 m x 2m) and there's a small cabinet for veg plants from seed/clones. Otherwise there's almost nothing else in the room.

So, I've been growing Morning Glory's pretty well for some time and for a while now this thing is going on (with the curled leaves). Although it hasn't made much difference in quality of the bud, still it makes me sad that my ladies feel so bad and I want to make them feel better, more like home.

Here are the pictures (1 with my growbox, 2 with close-ups from Malawi Gold and 2 with my newborn Blue Mystic, that's having the same problems as the others, including my friend's girls):

Ok, so I'm having problems posting individual pictures, so here's the link to the gallery:

http://img256.imageshack.us/g/dsc02806x.jpg/

whats 31 in f? i dont know celcius. you need fresh air in there get a intake and outtake fan and an oscilating fan. your humidity seems kinda dry too.

Yeah, but i have NOWHERE to get the air from. That's the problem. I'm keeping the doors open as much as I can and I am opening the window at daytime, but nothing changes much. At night I can't keep the window open because it's autumn and they'll freeze there. And I have circulating fans in boxe's, but none in the room, as they're really loud, expensive and if I montage them it will be very obvious that the room is not for storage. That's the problem.

And about humidity.. I had 50-60% at day, but I'm trying to lower it to prevent bud rot. It seems that girls like the lower levels of humidity, so I'll leave it that way.

so the seedling are on 12/12 too? your right on the humidity part, my mind wandered and i didnt notice how far into flower they are. whats 31celsius in farenheit?how often do you water?

I can't say for sure. I know that max recommended temps are 30 at day and 26 at night or so. I water as frequently as is needed. Trust me, it's not overwatering.

What else I thought - maybe it's too much co2 in the air? because I have two 5l bottles of co2 all the time. I can't remember for sure, but I think that when I put those there, this all started.

c02 is unneeded during the dark. maybe try running only one during lights on if u suspect it is the culprit. see if it makes a difference. what kind of soil is that and whats your ph, feeding them? what kind? how much? do the leaves feel soggyor crispy on the wilted discolored parts?

As I understand, co2 doesn't come out of the wheat mixed with sugar and water, if there is no light. But I am going to take one of them out, and look if it makes a difference. My pH is stable so I don't check it, ever. Soil is cheapest one I could find, with perlite, mix. I use Hesi nutrients according to schedule and that is fine. Leaves feel crispy where they're curled.