Do lawmower blennies and tuxedo urchins compete for food?

[LeanneP]

I've had a lawnmower blenny for about 3 months and he has always been really fat by the end of the day from eating. I bought a tuxedo urchin about a month ago and I've noticed that the blenny is getting skinny now. Is the urchin eating all his food? I have lots of coraline algae on the rocks and there is algae on the glass but I am worried he isn't getting enough food now. I've tried feeding him algae sheets but he not interested. Do they normally eat coraline algae?

Leanne P