At first glance it looks like carp pox, but looking more at the pics it looks like Hikkui.
How old is the Showa?
Is it only on the beni(red) of the Showa?
Is this the first time you netted up the Showa and notice the problem?
"One polyp looks like it is empty the other yellow."
In general this is a sign of Hikkui, no real cure of it.