Sounds like Brady has had quite a lot going on recently, between being in a shelter, finding a new home, the surgery and vaccinations (which ones?), meds (what were the drugs?) etc. Could be that all the stress has taken its toll on his immune system and maybe he just needs some time to recover and settle in. Supplementing his diet with a good quality fish oil is a great idea as the omega3 fatty acids are anti-inflammatory. Hope he's feeling better soon!
"To close your eyes will not ease another's pain." ~ Chinese Proverb
“We must not refuse to see with our eyes what they must endure with their bodies.” ~ Gretchen Wyler