Did you find anything out about Coqui's plucking? Hope the vet was able to give you some answers & can find a solution to help the dear girl get over this.
Roscoe started that same thing about a month before he turned 1 yr old & only did a small bit on his chest for about 2 yrs. Then it was a little bit more & a little bit more til he now keeps his whole chest & legs on the front plucked. Occasionally he lets them grow out a bit & then plucks it all out. I have come to the conclusion he just likes to pick at the feathers. He is the normal macaw and the only bird I have ever had who plucks. The other 3 macaws who have the degree of disability issues don't pluck. And in my personal opinion those 3 should be the ones who have every right to feel the need to pluck~~Go figure!!