So here's what's going to happen lol. The temps are not the issue, the mold that is caused by the moisture staying in the buds will be. With the cold temps the moisture will be trapped in the buds causing them to rot. Keep an eye on them and check the buds carefully, concentrate the search near the stalk, they will turn brown. When that starts to happen you will need to pull them or lose the whole thing. Plants will survive at anything above 0c. It will be wise to shake off any moisture each morning if possible. Covering the plant is not required and may make mold issues worse imo. Good luck and also just keep feeding them as you normally would.