Foxface venom?

Just earlier I was looking at my tank and I found my Lawnmower Blenny on its side dead. It doesnt look like it was a normal death because its entire underside was swollen. The Foxface that I also have in the same tank seemed really agitated and I've heard that their venom does make things swell. If anyone is able to confirm/deny what I think that would be great.

Side note: There are plenty of other fish in the tank but none venomous.