Hmm. I guess he may be having trouble with the psychological aspect of weaning then. A few days ago I saw that slight head bob and was terrified that he was regressing but dismissed it since he was already eating well on his own, but what you're saying makes sense and corroborates my earlier concern.
I've already put him to bed for the night, but tomorrow I'll offer some ground up pellets with hot water to see how he reacts. He really has no trouble eating the food in his bowls, but if he starts acting like a baby being handfed, I'll grab a bag of formula after work. Getting to the breeder for help would unfortunately be a bit of an ordeal, but luckily I learned to handfeed a while back.
Thank you for your suggestions!
Right now he has several millet sprays in his cage, all in various states of being eaten.
His poops generally reflect whatever he's been eating... usually they're greenish or light brownish but there's been quite a bit of blueberry poop going on!
The chewing I was referring to isn't the cute happy beak grinding, it's a total insistence on gnawing any bit of fabric he can grab! He's absolutely obsessed with shredding fabric. I wish I could put some in the cage with him, but the risk of getting caught in a thread is just too high.