I have had two cross beaked chickens before. It wouldn't be nutrition-related after they were hatched. IDK if it is genetic or nutritionally related (for the hen before the egg is laid).
What I would recommend is to definitely check them over for mites/lice and dust them if needed, retreating at 10 days for mites/2 weeks for lice.
Additionally, I would feed them lots of protein...consider feeding them scrambled eggs and plain unsweetened yogurt for treats.
You might consider even buying a 20% nonmedicated chick starter feed and giving them oyster shell on the side for calcium until they have grown their feathers back. Making new feathers requires a lot of protein. This will help them through their molt and hopefully get them laying again faster.
Molting is very hard on hens.
In terms of heat at night, if you are giving them a good coop that has no drafts but good ventilation (no air blowing directly on them) they should be fine. But you know your setup better than anyone else. I do give heat (100 watts) when we go below freezing.