I am so sorry to hear about your cat.
My co-workers cat developed a blood clot in his back leg and was in horrible pain. There was nothing to be done but have her precious baby PTS, diet change would not have changed the outcome. I do believe this may be caused by a heart defect.
Cat maid to:
Jasper, male Ragdoll ?? (approx 10 yrs)
Rose semi feral, a cpietra rescue, female tabby (approx 7 yrs)
Sweet Pea RIP (2004?-2014)
Puddles RIP (1996-2014)
Snowball RIP (1991-2005)
In a cat's eye, all things belong to cats.-English Proverb
“While we are free to choose our actions, we are not free to choose the consequences of our actions.” Stephen R. Covey