What's wrong with Casper's cere?

Hi, this is my first post on Talkbudgies, so apologies for any errors!

I have a 2 male budgies, Link and Casper, I've had them for just over a year. Casper is roughly 18months old now and has developed a strange growth on his cere.
I've tried attaching a photo of Casper to give you a better idea. I took it on my tablet so the quality is dreadful, I'll try upload a better photo soon. It's not particularly flakey or crusty as growths can be- from what my research into it has suggested. It has developed from the lower cere over the last few months,it's very pale, and it doesn't seem to affect him in any way. It actually just looks like an extension of his cere growing out a bit to a point.
What is interesting is we took him to an avian vet a month or so back for a swollen eye (he had a feather in his eye and had rubbed it sore overnight). The vet did a general checkover of him and said he was in great health, and never mentioned his cere. I was quite upset that he had hurt himself at the time and didn't think to ask about his cere.
I've looked into it and the only thing that has really cropped up is scaly face mites. A lot of people have said the fix for this is rubbing vaseline over his lower cere. Obviously I don't want to be rubbing things in little Casper's face unless I'm sure, so I'm interested to know what you guys think. Should I go back to the vet? It seems like if it was something serious she would have mentioned it on our last visit.

Thanks so much for any advice you can offer as you can imagine I'm really worried about the lil guy.

Emma