Sad clones after 3 weeks adjusting to flower

Hey guys - Here's the deal:
4 Tahoe OG Kush clones
1000 hps
79* high
42* low
45% RH
1000ppm Lucas formula
Bloom boost
Aero/hydroponic Rubbermaid
4" net pots

went right from the club shelf into 12/12 flower.
One of the plants is doing way better than the rest, but 3 are sad none the less.
The roots are great! No problems there.

The problem is they're droopy, and some of the leaves are turning purple/black color. Is this from the cold temps?
Also not much growth besides roots in the past 3 weeks, although they seem to be transitioning into flower just fine.
They're basically the same size as when I first got them.

Is my problem that my temps are too cold? I didn't think they'd have an issue with it but that might not be the case.

I just don't see a heater worth it when I've only got 4 plants. (cost wise)


Anyways here are some pictures

http://img.photobucket.com/albums/v602/crfiddyryder/Mobile%20Uploads/image-2.jpg

http://img.photobucket.com/albums/v602/crfiddyryder/Mobile%20Uploads/image-1.jpg


And this one being the healthiest:
http://img.photobucket.com/albums/v602/crfiddyryder/Mobile%20Uploads/image.jpg

What do you guys think?
Thanks in advance!!

Quick question, do the plants look pretty good when lights r on and then in the dark cycle look like total shit?

They pretty much look the same all the time.

If anything the leaves are slowly SLOWLY turning more upwards. But this isn't my first grow, these are just problems I haven't had before! Hmmm