@rockulius, I just thought of something - do you have a chlorinated pool? This reminds me of someone elses duck on here that had been swimming in a chlorinated pool every day. Maybe the cut started something, or accelerated something. Just a thought. I will see if I can find that post.
Here it is - doesn't look exactly the same, but it was worth a try -
Edited by jducour - 10/12/15 at 8:54am