I grow in an unfinished Michigan Basement and night temps easily are as low as 64 F when my lights cut off during the winter. Daytime temps I let rise as high as 80 F at the canopy. If you take a temperature gun and shoot the buds with lights on the stalks will be around the air temperature ~75 F, your growing media/rootzone should optimally be around 68 F at least in my couple years of experimenting in a sealed grow with no ventilation and co2 supplementation (Liquid Propane Titan Atlas burner) and 3 ton mini-split head to 6 1000W Gavita.
Personally I think anything below 60 F is dangerous and can cause stunted growth or other issues such as powdery mildew, especially if your humidity is above 50%, period. You can get powdery mildew when its dry too but its a lot harder than when its moist and cold air.
Considering your temperatures I'm assuming you're running LED lighting because your temps are not getting very high at all. Just so you know, your plants will "pray" and perk up if you heat that room up to 75-78 F guaranteed. Without they will be kinda laying down, at least in my experience literally just walking downstairs into my veg room and it being 68 F in there with lights on.. : To get your temperatures higher you could consider adding T5 lighting which puts out a decent amount of nice warmth. I regret not keeping some T5 lighting in my veg room because now I do have the issue of it getting too cold in there during the winter months..
Heaters in gardens are risky business, you can dry the air out too much so you need to select the correct TYPE of heater. The best heaters are going to be oil radiator style heaters (they have no lights and put off no dry air) and or a mini-split Air Conditioner with a heat pump.. (Very expensive, hence why I let my temps drop to mid/low 60s no problem, literally saves me hundreds of dollars per/month..
What equipment do you have in your room running? There are a lot of ways to improve the room depending on budget, space and spare time you have to offer to your garden. One friend of mine just built a mega insulated room 360 degrees and keeps his temps 75-68 F 24/7/365 with no problems..
I'd do that but again I'm in an unfinished basement and not looking to spend $2,000 on a properly built and insulated room like that. I'd rather spend $2,000 on new lights, another dehumidifier or hell even another mini-split air conditioner unit...