Yes, chicken could be the problem. If it were just shedding with a little itchiness, I would say it might be the time of year. Dogs usually shed twice a year in Spring and Fall. If it is a lot of itching, I would switch to a grain free/chicken free food. The fact that each time you switch you go to a higher quality food and he gets worse, makes me think chicken because higher quality usually means more meat. If chicken is the problem, more chicken would be a worse problem.
Rotating foods is important for gut health, but first you need to get the other thing straightened out. Unfortunately, a lot of foods have chicken in them that don’t have chicken in the name of the food, so you are going to have to carefully read ingredient lists to make sure the food you choose has no chicken in it. If going chicken free for a while solves the problem then you can start rotating again, just stay away from chicken. If it doesn’t then you will have to try to eliminate other things. I have one that can’t handle most grains and chicken. Good luck.
