You did all you could... maybe it was for the best in the long run. It's tough to see 'em go.
Our last cat was a runty thing, had on going problems and ended up with siezures, we probably tried too long with different medications but you don't know til afterwards.
You can only do your best and what your heart tells you.
Our current cat had an argument with a car (we think), she's going to have her tail amputated soon, her bladder control isn't 100% (but hey, I expect I'll be there soon myself!) But she's back to her old mischievous self
Hope the rest of 'em thrive.
Del