pleco deaths

[famman]

I've lost 3 pleco's in a row in my 55 gallon show tank. The pH is 6.8, kh 3, temp 78F, I use DIY co2 and an eheim 2233 filter.
The other inhabitants are a pair of spawning angels, 6 black ruby barbs, and 1 golden inca snail. No other inhabitants have died, just the plecos. Symptoms may include a large belly, discolored and darkish.
Decorations include a large piece of sand-blasted grapevine wood (my prime suspect), live plants, a few pieces of ceramic pottery (a secondary suspect), Tahitian moon sand. I use a 110watt cf for light.
Anyone have any ideas why?
I'd sure appreciate the help, suggestions, etc the board would see fit to provide.
many thanks,
:)

[RTR]

Are they "polishing" the wood? If so, that would be my prime suspect.

Is the pottery a low-fired import? Does it show any erosion of the decoration/color? If so, it would be my back-up suspect as well.

I'd remove both and try with regular sand-blasted "driftwood".

[famman]

Thanks RTR,

Yes, they are sort of 'polishing' the wood. Even the snail got sick for a few days (as if you could tell when a snail is ill). I've already removed the wood.
I'm not sure how to tell about the pottery. It appears to be well fired and glazed pottery, I felt very confident at the time that the pottery would be safe. Of course after a fish death or two your confidence erodes.
thanks
:)