donrae
Rest in Peace -2017

My first thought is also a space issue. How large is your coop and run, in feet? And what breeds are you dealing with?
Can you post current pictures of your birds?
You've had them about a year and a half. This is the time when most birds molt, that could account for the feather loss. Is egg production down also?
Have you checked them for mites?
What specifically are you feeding them?