black/blue stomach on plecos?

[xdragonxb0i]

well i had a bad week 2 gold nuggets pleco died today and one die on arrival a 2 weeks back.
is that an internal parasite, when their stomach is blackish blue when they die

http://www.monsterfishkeepers.com/forums/attachment.php?attachmentid=331267&d=1236044828

 

[xdragonxb0i]

bump
just found out that the link is wrong