Hello & welcome, Karen. I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Was Tinker exposed to your previous FIP kitties? Was he ever tested for coronavirus?
What did his vomit look like?
Can he keep water down?
Are his gums pink or pale/white? Moist or sticky?
If you press on his belly, does he have any discomfort, tenderness, or tensing?
Could he have eaten something he should not have (ie bones, string, plants, chemicals, etc)?
Has he had any diarrhea?
Has he responded at all to his vet's treatment?
Did they do any tests?
Did they use any anti-nausea treatments?