I had him for 2 months. There were 3 other plecos in the tank - 1" bristlenose. And then some tetras and cories.
But I think I have figured out the problem since. I had switched from a HOB filter to an Eheim 2213 during that period and after one water change, I had overfilled the tank so there wasn't enough surface agitation. I have since raised the spraybar and replaced that little L128 with 3x 1" L066 to grow out and so far no problems. I also got 5xL128 which are much bigger (4") in my 125 gallon which are doing great. So hard lesson learned.