Can you please tell what is going on with my chickens throat? Balding??

Is this the start of molting? I have been putting aquaphor ointment and it looks alot better but she is bald now!! We lost a chicken a couple of days ago. Could this be related?? I treated them for mites with sevin dust and 10% perethins spray. I did not see any mites but i treated anyway. She is the only one with this balding and the other 4 chickens seem fine?

Has anyone seen this before?