This is not a standard test - so although your bird has had regular blood tests, you might want to ask you vet about this test.
Sprouted sunflower is also nutritious, as is quinoa, brown rice and beans.
You may also wish to discuss photoperiod with your vet - daylength is thought to be one of the natural signals that helps a bird's body to know when it is time to molt, breed, etc. It is possible that he may be sensitive to artificially long daylength caused by inside lighting. Be sure to let us know if any of these ideas, or a combination of them, help your boy with his molting difficulties. Hope these thoughts have been of some help to you. My S.I. male that is 6 yrs.