I have not tried it, but was told by a very experienced breeder that when the toes curl after a chick is on the ground it most likely is caused by a calcium deficiency and can be fixed by adding calcium in the form of ground egg shells. He said that he had never seen egg shells in a nest where the chicks were hatched naturally. Just don't overdo it.......Curled toes is an odd case. The most common cause is incubation problems. What is your incubator and were they shipped eggs?
Another cause is vitamin deficiency. If the feet start to curl, try supplementing with Vitamins, especially if you are using medicated feed.
Another thing to consider is the curled toes can be corrected and are not live threatening.
If it is Genetic, It is likely due to inbreeding and could be corrected by out crossing to a not closely related flock.