koi with red lesions, disease ID?

[Mahi27]

Hi everyone. I feel like every time I post on this forum it's because I've got some drama. Sorry about that. But please help if you can to identify what's wrong with my buddy, Jose Cuervo (don't ask). Pics attached.

I know this is mostly an indoor aquarium forum but Aq Co-Op people seem to know diseases and treatments better than anyone else.

Pond parameters:
Size and stocking - ~750gal, 8 seven-inch shubunkin, 1 four-inch koi, 1 eight-inch koi (Jose)
pH: 8.0
Ammonia: 0.1
Nitrite: 0
Nitrate: 0
gh: 80
kh: 180
Last water change: Yesterday, 50%
Temperature: Stays aound 55 F 

 

Background info: Early December I noticed Jose Cuervo's friend, a juvenile yellow koi named Lemon, floating near the surface in a low-flow area of the pond whenever I went outside. I also saw him flash on the substrate once or twice. Three weeks later, he had disappeared (I was busy with holidays and unfortunately he paid the price I guess). Now I am seeing Jose Cuervo doing the same thing -- floating in the same low-flow spot, super lethargic, not really eating.

Yesterday (Tuesday) I dosed the pond with 6.25oz of PraziPro (at a rate of 1oz/120gal). 

Tonight I saw Jose sitting in the same spot for at least an hour. I went and netted him out, which was easy due to the lethargy. As you can see from the pics, he has some red stress streaking in his pectoral fins, but the base of his tail has red sores on either side and his scales are pineconing a bit (as if the area is swollen). 

Can anybody help (1) identify the disease(s) afflicting Jose and (2) recommend a med regimen to help? My thought is external parasites with a secondary bacterial infection, but another set of eyes will really help me out here.

Thanks.

[Colu]

I looks like a bacterial infection  I would treat with aquarium salt 1 table for two  gallons for 5days if no lmprovement try maracyn or maracyn2