Weird growth on my African Grey's beak

by Clve
(Devon, Uk)

I have recently inherited a 3 year old African Grey and he's got this weird looking growth either side of his beak, it seems to grow and its fallen off a couple of times, just to grow back again. He also stopped talking all of a sudden about a year ago and he's also had watery poo for roughly the same amount of time. He's just started to lose some feathers too but I'm sure he's not plucking them, what could it be?