Plants starting to veg again in flowering light - why?

Hi guys, I need your help.
Long time reader, 1st time poster.
I have been growing Skunk No1 for a while with little problems. A couple of months ago a batch started to flower (12/12) a few weeks in & then stopped & started to grow again. It was cold so i added a heater, changed the bulb & started the next batch.
This time they showed less flowering before vegging again.
I smoked that lot & started again.
Bought a nice new 600w hps solarburst. Dropped the cycle to 10hrs light.
this time I havn't seen any flowering at all.

Can the cold do this? It freezing at the mo & drops to 67ish regularly but sometimes as low as 58.
I have my clone box in the same room but have ensured there is no light leaking tho.

I have not changed anything on how i grow since i started & have not had this happen before...

Any ideas welcome as its months since i had a good batch come through

Im wondering about this too, I had this happen to a batch of mine, and 1 or 2 have it on my current batch. It did happen to mine as it got colder, and I didnt realize it was gettin a little too cold in my room. I dont understand it. Sorry im no help, just wanted you to know your not alone.

I've noticed a differance with temp at night when lights are off i got myself a small room fan heater i've put it on a timer so it comes on for 20 minutes every harf hour and things are starting to happen now i even use neater sometimes during the day its been fucking freezing.But i've one on a 24 hour sycle bang at side whitch is helping with a little warth.But it is important to keep you plants warm during lights off has it is during lights on.Put the heater on a timer so room don't overheat and it coses a fortune in money.And make sure that light is not getting in from any where else.

Cheers guys I have just put my heater on at twice the rate to keep the place warmer 24/7.
Fingers crossed as this is getting annoying

Any light leaks or interuptions??