Hey guys! Sorry it took a while to get back, today has been very draining.
He hasn't lost any weight, he's 609g, the same as mid April and even up 30g since February when he lost his appetite (probably from the herbivore emer-aid, butternut squash baby food, etc)
Emergency vet has put him on an antibiotic injection and eye drops for the next little while. I have a follow-up visit with my regular specialists on Friday and will update then.
He is currently doing well, which I'm so happy for.
Thanks for everyone's input, it was comforting to have people help brainstorm causes and solutions