Depends on how often you're feeding them pinkies. If its very infrequently, and they're getting mostly fillet, then yeah, go ahead and use a supplement. A very light dusting on one bite of food once a month or so is enough.

I think Steve can recommend a multi supplement. Like I said, I don't even use them. Even baby snakes get whole pinkies from me. Even if I have to chop them up and mix with fish.