What are your water parameters? (ammonia, nitrite & nitrate). How long have you had the bristle nose? What else can you tell us about your tank---size, all fish & how long you've had them, water change schedule?
What, besides veg on a fork, are you feeding? He looks nicely chubby. I see what you mean on his upper side but I agree with OG, not alarming. Do a few water changes within a few days & see if that helps.
Hey thanks for the help but he is starting to go back to a good solid colour now think it might have been a bit of stress I put a new cave in the tank a couple day befor the change and found out it could have caused some stress all water reading are fine had them in the 4 foot tank about 1 year now I feed them algae wafers cucumber and some other greens as well think thanks for the help
Continue to give proper care to your BN as it seems you are doing, and you may enjoy them for many years. I had one of them for 11 years (my personal record with a fish). I still miss that little fish!