Mysterious Death Of My Pleco's

[Johnny Pea Head]

i've purchased 2 pleco's over the last 12 months and for no apparent reason they have both died after a few weeks in my tank. Both were fine one minute then dead the next??? Both of the fish were purchased seperately, the second one a couple of months after the first died. All of the rest of the fish including my bronze corydoras are fine. I was feeding them the special plecostomus food but neither of them seemed interested in it, even if you dropped a tablet next to them. They just seemed to feed off the algae on the glass and nothing else. Can anyone help? I don't want get anymore in case they fall victim to the same mysterious death! Like I said in both cases they were fine one minute then dead the next.

 

[WILDER]

Well i feed mine veg as well, were they bloated, or thin with a sunken in belly, any colour change before they died, what colour was the poo when they went to the toilet.
Was there anus enlarged or red and inflamed, did they lay on the bottom of the tank to one side.