Good news.
One of our cat’s comes over as a tough nut, never ill, but a few months ago wouldn’t let you near her, pain in her back, growling and whimpering if you tried to pick her up . Checked over by vet for RTA etc etc, nothing. Most likely a slightly infected bite from the new kitten.
The ‘kitten’ is now bigger than the other cat (he’s 1) and it a right hard nut – headbutts stuff, been stung on his paw and it was twice the size of the normal paw – didn’t bother him other than a limp. He’s a pedigree though, and the particular breed does appear to have a high pain tolerance.
The tortie is a wimp.