Did my rooster have a disease? (non-emergency)

[WDFlock2015]

I'm a backyard breeder and we recently processed the excess birds that have collected over the hatching season. We also included my Gold Laced Wyandotte rooster that was for breeding because of our failure to attempt to correct his behavioral issues for several months. When I dressed out this rooster I found a significant fat layer at the cut sight (more than usual, and more dense) and as I proceeded, discovered additional fatty layers on every internal organ, including the intestine. I am fairly new to chicken raising and processing, but this is the only time I've seen this after having processed approx. 50 birds from ages 8-16 months. Is this a type of disease? Is it genetic? Did it contribute to the behavioral issues?

I appreciate anyone who can shed some light on this for me.