Lily our yellow, is soon to be 13, and we ve noticed quite a slow down physically in that she can't walk very far especially on hills. Gets very tired and slow. Vet found a heart murmur last summer that we don't think has been there all along. So shorter walks it is! Also notice her hind end is weak when we brush her or towel rub, she has very little strength. That's new since winter. Also can't support herself if she tries to turn quicker while jogging, or leg steps out or slips out. No limp, no stiffness in morning. Is this what muscle wasting behaves like? Thanks!