Sorry that you lost Fashion. I started doing necropsies on my hens that died several years ago. The yellow poops can be a sign of infection in the reproductive tract. If the urates are yellow, that points to a liver issue. Liver disease that causes ascites can be from egg yolk peritonitis, liver cancer, fatty liver henorragic disease, or heart failure. If you open the abdominal wall and yellow or amber fluid comes out, that would diagnose ascites. But the root cause could be any of the diseases above. One hen I had died of fatty liver, because I saw ascites fluid, a tan liver, and a large blood clot uder the liver. It’s good that you are aware that feeding too many treats and overweight hens can be causes of fatty liver. I don’t know of any treatments, and you just never know until you can look at the organs. Hopefully, Izzy will live a long time.