I lost my cat to Fip, there is not a test to rule this out without dooing ultrasound/xrays, and that will not give you a definate prognosis until after, saying that, my cat was not sicky, early symptoms are inability to walk on four legs, (neuralogical) she would often hold her front paw up, + when you looked at her in a sitting position she looked abit wonky. + normally it is within the first 2 years of life or the later stages in life. I hope you get a diagnosis soon but from what your vets are saying i do not think it's Fip.
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