5 week old ringneck closing eyes during feeding session

i have a 5 week old indian ringneck and i’ve been such a stress case ever since i got him on monday. i took him to the vet on wednesday because i was hearing sneezing, although no discharge, and it freaked me out. the vet said his lungs sounded clear and his vitals were good and she prescribed an antibiotic, which he’s had 3 doses of and has 7 seven days left on. at 1 he had his most recent feeding, and i noticed he’s closing his eyes while i’m filling up the syringe with more food. i texted an avian vet service and a licensed avian vet told me this is normal and shouldn’t be a bad sign. he ate pretty eagerly, and cried very loud for his food, but i’m still worried. i’ve been SUPER careful with literally every aspect of his care because i’m so afraid his immune system isn’t strong enough to handle anything happening. my green cheek passed a few months ago due to a respiratory infection, and i couldn’t bare to lose this little guy too.