Thanks to everyone for their good wishes and advice.
Took Max this morning to the Vet and they weren't too hopeful considering his age.. My wife reminded me that he's actually 29! Without the Vet doing more in depth testing, prodding etc they really wouldn't be able to diagnose what's really going on. And we don't want to subject him to all that, considering his condition and age. They believe it's neurological - (he's had some difficulty perching recently and falling in and out of his cage) amongst other possibilities they discussed ie; certain organs breaking down, maybe had a little stroke/ or has a brain tumor, etc. Just guesses at this point. So, they prescribed an anti-inflammatory, which we just gave him. And, they also gave an antibiotic, which we held off giving him. So we'll see how things go in the next coupla days. But all in all, we're not very optimistic, again due to his age. I think we just have to face the obvious and make sure he's not in any pain or suffering before we make the final decision to have him enter the rainbow, while our hearts break into pieces.