2 Koi with several problems 1. White?, missing scale? black mark

Goldfish lost scales and turning black : r/Goldfish

Black spots on koi someone please tell me what is it? : r/Koi

missing scales

Comprehensive Guide To Goldfish Diseases

Koi (shusui) has scale issues - Koi-Bito Online Koi Forum

Troubleshooting Unusual Pond Koi and Water Quality Problems - POND Trade Magazine

KOI AND GOLDFISH SPAWNING IN BACKYARD POND IS EASY TO RECOGNIZE.

missing scales

Koi Symptom Diagnosis > Hanover Koi Farms