3 young chicks that can't stand up

My husband purchased baby chicks a few weeks ago from a local feed store.. Not something I would have done and I have assumed responsibility to take care of these babies.. It has been very cold out so they have taken up space inside our home.. I clean there bedding out every day.. They have fresh clean water and clean food from a feeder.. Also have two red light and plenty of space out of the light if they get to warm
they can move around.. The nights here have been in the 30-40s and I didn't want them to get to cold.. I have older chickens whom have done fine outside.. We have been raising chickens and using the eggs for years and I have never had a problem..

Until now.. I have 3 chicks that can not walk. They appeared fine up until the last few days.. It's started with one and now 3.. I fear it's Mareks.. When I stand them up the just fall face first or try to stabilize using their wings.. They also seem to keep one foot curled up.. No signs of injury.. Not over crowded..

I can't see them suffer.. Please let me know what I can do..

The feed is crumble chick starter

You're right in being concerned it could be Marek's. To have three chicks all with the exact symptoms, certainly is telling.

You need to get them away from the other chicks asap and look into treatment for the entire bunch. I have no experience with the disease, but I do believe there's a treatment for it. Ask a vet or go post on the "Emergencies" forum for advice on what you need to do.

it could also be a vitamin deficiency.Especially in younger chicks. can you post pics? Mareks seems to present itself in certain ways and deficiency in another with the same result as a inability to walk. a pic might help decide which is the issue. are the legs stiff and feet curled? are they in odd positions? I'm so sorry for your birds. we're they vaccinated against mareks?