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Due to the young age of your rooster, I suspect a vitamin or mineral deficiency. I recommend Avian Super Pack. Dosage is 1/4 teaspoon per gallon of water. Here's where you can buy it:
https://www.jefferspet.com/avian-super-pack-100g/p
Excellent video!
I suspect the scaly leg mites have caused tissue damage in the legs. Given time, they can eat right through a leg. I'm glad you're treating the scaly leg mites.
The blood sucking mites probably took a toll on him as well. Left untreated they can cause anemia, then death. The...