That is surprising. I have never had Polish or Silkies bother each other's crests. Maybe it is a space issue or needing more protein. They will pick and eat feathers when lacking in protein. I like to feed all my birds Purina Flock Raiser from newly hatched chicks on up to adults.It looks like the one polish is doing to the other polish. Guess I need to separate them.
The white one s head look worse this morning.
Good luck, hope you can find a solution.