Sadly, I found my lawnmower blenny belly-up on the bottom of the SB this morning. I examined all his fins and did not find any damage. His belly looked bloated -- which isn't surprising as he ate all the time. I did not see any white specks or anything.
I have no idea what could have happens except maybe he ate too much. He lasted for 8 months and seemed fine, no aggression from other fish.