Burds are master's of hiding illnesses. This is hardwired by evolution, as sick burds are turned in and driven from the flock. Sick burds are targeted by predators.
Its harder on us humans to grasp instincts and hardwired behavior.
Birds often don't show what we think of as classic " sick bird " symptoms such as fluffed and down on bottom of cage till near death like hours from death. Some birds death is the only "symptom" even tho they were sick for weeks or months.
My gcc had one day of a few clear drops from one nostril. She was dead the next day. She never stopped eating or playing or vocalizing or fluffed. She had a past history of intermittent sinus infections , so I was going to take her to the vet the next day, I just didn't get the chance. She did end up having a sinus sbcess....my poor sweet girl.
So when we give advice to go to.the veterinarian with any symptoms its because we don't want people to loose their birds. And there is no way for us or you to really know how sick? It bites to spend money and find out they are fine, but I'd celebrate that, rather than tears over a death i did nothing to prevent.
BTW when I've ever had symptoms like excessive sneezes mine have always been sick. I've never been wrong to be concerned about minor seeming symptoms as they have always turned out to be sick. But I'd have been happy to hsve spent the money and been wrong !