Low Nite temps

Ok, My current setup is a good drip system. Res temps are between 66-72. Day temps for these plants are between 72-76. Im having trouble with the nite temps though. Currently its around 55-58. Is this ok? would it bee fine for the rest of the time (approx 4 weeks) There is no way to put a space heater in the chamber so thats out. I had a space heater by the intake for the air, but i really dont want to leave it running all the time. If this is ok for temps then good, but was wondering if i would see slow bud growth or just slow growth in general. Thanks all.

These are normal fall temperatures,
and the plants will do fine.

Nothing to worry about.

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ok.. i know that alot of stuff i read says not to go lower than 60, but if you say its cool then it must be cool.. thanks for the reply

Get as much light on them as you can.

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I have 2 430W hps bulbs on them. Is that enough?

if you keep under 70 you get the chance to get more males!

ummm.. out of 18. i have 14 females and all the males have been pulled... but thanks for the concern I thought that too though in the begining, but as i said i cant put a space heater in by them. I was worried for like 3 weeks about the male/female ratio, but now i just laugh because Im soo lucky. 14 out of 18 is steller in my book