Bn Skin Problem

[mbeer21]

My 3 year old Bristlenose Pleco has had this weird skin discoloration on his back for 2 days; he also seems a bit lethargic (though he is eating).  
 

 
I have lost two tetras in the past week, but I'm not sure if that's related to this as I haven't seen anything similar on those tetras.
 
I can get water stats when I get home from work if need be, just checking if it's something that can be 'diagnosed' just from the photo first.

 

[ShinySideUp]

It looks like the catfish has been injured. I had a similar thing on my BN catfish a few years ago after he nicked himself on a rock (I presume). I believe the white stuff is a kind of mucus that the fish exudes in a similar manner to the way people with cuts form a scab but obviously underwater a scab would just become soft -- the mucus is the fish equivalent.
 
If it is indeed as a result of injury you should see it disappear perhaps after a week. IMHO it shouldn't get any bigger from it's present size, if it does it might be something else less innocuous.

 

[mbeer21]

That's good to hear - I'll keep an eye on it to make sure it doesn't get any bigger (so far it's gotten a bit whiter, but doesn't seem to have changed other than that).  Thanks for the help!