it is alright to have the fan on during the dark period only

i am growing two plants in a greenhouse and i am two weeks into flowering. To flower them i just bring them inside at 10:00pm and take them out at 10:00am for 12/12 cycle. I need to use a fan because the stems are looking thin and weak BUT there is no power in the greenhouse. My question is.... Is it ok to just use the fan during the dark period? doesn't the most growth happen in the light??

sometimes i keep my fan on 24 7 depends on the stretching for me

i would say yes, but keep the fan on a low setting, you dont want it to blow all the resin off the leaves

ever notice that at night the wind can blow too? Ever notice all the plants dead the next day? think things will be different with a fan?