Hello - I finally got a picture now that it's morning.
He's been on vibramycin, and that took care of the fluffing, sleeping and general sick look.
Currently, he's chirping away, playing (he has gotten more interested than usual in tearing apart his grapevine balls, if that means anything), and generally being normal budgie.
He only makes the noise at night, generally when he's startled, like when I go to cover his cage. I will try covering his cage earlier, he might need to go to sleep earlier. The sound is like a cross between this one, which I found on a web page about avian sinus infections (https://www.birds-online.de/verhalten...les-atmen1.wav
) and his normal chattering-to-himself sounds.
Not sure what's with that. He doesn't have a crusty cere and isn't losing feathers around his eyes as per other sinus infections. And he sits up normally, doesn't sit in a weird position that looks like he's helping his breathing, and his poop looks normal.
The vitamin A would make sense - back when we took him to the vet the first time for the general sick look, they suggested a deficiency, but we haven't yet figured out what vitamin he's missing, I guess. I've gotten him a mineral block for iodine, he already had a cuttlebone, and I've started putting sunshine factor in his food for vitamin A. I could certainly add vitamin drops to his water as well. And I do have probiotics left over, so I could give him those as well.