So Kale has never had what one would call smooth plumage. But lately (1.5 weeks) he has been looking a little worst for ware. We're wondering if this is a condition or whether he's just going through a severe molt. Obviously, he's the one on the left.
You need to be very aware of your birds' behavior to determine which one is causing the feather loss.
From the location of the feathers, my guess would be that Kale is plucking them out himself.
I would suggest you get the bird to a good Avian Vet for a check up to determine if there is an underlying nutritional deficiency and how to best help Kale recover.
Avian Vets have special training to determine the cause of symptoms resulting from illness or trauma. This is important as "regular" vets will often overlook symptoms that are quickly obvious to an Avian Vet.
When you rely on anyone who has not had training in Avian diagnosis and care, you may be delaying effective treatment. This can prolong suffering that may be avoidable.
The bird will often require a more intense, prolonged treatment with a poorer chance of full recovery than it would have if you seek prompt professional diagnosis and treatment at the first sign of illness.