2 hens weak legs, NOT MAREKS

I have had one chicken who has had weak legs off and on since she was a pullet. Every time it started, I treated her with calcium and she recovered. She is 18 month and molting now. Her legs are pretty weak now despite me making her rest and take calcium. Now another of the 18 month chickens in molt is showing the same signs. This one has never had this before. Their outdoor run has a roof but sun shines in. Treated for mites this summer. No one seems to have mites anymore. It is like their hocks bend outward when they stoop to peck and when they stand up they walk like they are dizzy.
They eat Purina Layena and free range once in a while.
Could this be worms? I haven't seen ANY in their poop. If it could be worms, it is okay to worm them while molting. Can't take them to the vet and I'm at a loss. PLEASE HELP!!
Could it be something else?

p.s. I have seen Mareks and this is not it. This is a reoccurring problem over the life of the first hen.