One of my torties, Turtle, seems to be going gray. Normally, she is a very strong orange/black/tan colored tortie, but I've noticed patches (especially where she pulls her fur out in clumps which a cannot seem to stop from happening) the under-fur is very gray. No sign of pattern, shading or washed out color. She'll be 5 this May, so it's not old age, but is it a sign of a health problem? Or does this just "happen"?