low temp nights

I have 2 plants in my garage. My light cycles is 10 am- 10 pm so the light keeps em around 65 but its been getting in the low 40s at night. I cant move em inside cuz of siblings and i cant add a heater cuz im already consuming a ton of electricity

 

Ok. Thanks. Should i slowly change the light cycle. Like 11-11,then 12-12,1-1 and so forth