lawnmower blenny skinny

I have had my lawnmower Blenny for about 6 weeks in my 32.5 gallon tank (long). The first 4 days it was in the tank it hid and didn't come out much, and would get scared if I came near the tank. I could see it grazing on the rocks at about the 3rd day I believe. It didn't come out when I fed...