We originally had an albino Pleco when we bought our first set of fish about 6 weeks ago. He seemed to be fine then all the sudden...he died. So we got another one about the same size but regular...the next day, he died. Now we bought another one about 3 inches long and this morning we found him dead. What is happening? FYI!! We have a fry of Molly's that are doing fine right now so the water is pristine!