Large breed dogs in particular, especially with nutritional imbalances, have this issue. The flooring means nothing. Flooring will not have THAT dramatic of an effect. Food however, especially calcium supplements on a large breed puppy going through rapid growth, will.
Yes, it could be something more serious that requires medical intervention, but it’s not the floor. I’ve never, EVER, heard of slick flooring causing pasterns to drop. Maybe flat feet or dysplasia issues, but your biggest issue is the pasterns and that is either nutritional or an injury.