The Wyandotte looks to be molting since she has some new feather shafts coming in. Or she could be growing back feathers she lost. The black mark on the comb is probably a peck wound. The feet do have a greenish hue in the picture, but it may be the light. I would stop the layer feed now, and let everyone have an all flock feed. The pullets are still too young for that much calcium. When they are 20 weeks old, you could start it back or keep them on all flock from then on. You will need to put out some crushed oyster shell for the ones laying to take as they need it. Continue the B complex for now.