Yes totally normal. Let them eat it too. It's how they reasorb vital nutrients. My big boys love to fight over slime coat when it's slime time they do it all together. My wife baby sits, and little kids scare the heck outta my limas so they shed then, or when there's no little ones about once or twice per month, but hard to catch them cause they eat it haha. Some of my favorite fish, so much character.