Anyone in 12/12 with lights on at night and off during day? Can't get mine to flower!

I need help. I have my grow area up in the open attic. I got a 12x6 area enclosed. The temps get anywhere from 70-90 degrees up there. I switched to 12/12 5 weeks ago.I have the lights on from 9pm to 9am and off during the day to help keep temps down. Using a 400 watt hps light. I discovered a couple light leaks at 3 weeks into 12/12 when they wern't showing signs of pre-flowering. Now 5 weeks since i switched to 12/12 they are still vegging.OMG! I think I've got to change them back to lights on during the day. Anyone with this same trouble? I don't have an air flo vent system set up to help draw the heat from the light out. I'm wondering how much it would help so that i could have the lights on during the day. Last fall I had the lights on during the day in 12/12 and had no problems with them flowering. Theres got to be more leaks that i just can't see.

that or ur timer is "on" and not auto? goodtimez

You gotta have a leak man.
I been running lights at night for quite a while now and have had different setups, when they wont turn its always a light leak.
I would say by adding air cooled hood you should drop at least 5° maybe 10°
There is always spray glue. Works great at sticking mylar to wood.