If the sanke looses all it's red, it will be a bekko. However, I think the red in the front is fairly strong and will stay. The red at the back will probably all go, and it might actually be better if it turns out to become a bekko.
The white fish is not a ginrin. It is a doitsu platinum ogon. Under the doitsu group, you get leather carp or mirror carp. Leather has no scales at all and mirror carp has only a few, either on the sides or dorsal line or both(like in your case) However, it is still a doitsu.
The black spots (shimis) on the kohaku's is a demerit and makes it less valuable.
I would rather say your one Kokaku is a Yondan Kohaku (four steps) than Sandan (three steps)
The one with the kucibeni has too much red and too little white, and I therefore prefer the Yondan Kohaku, although I like koi with a Kuchibeni (red spot on the nose)
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