Asriel’s nose and paws can get a bit greenish-yellow from greens mixed with water he’s been drinking. if that helps

My cloud gets this too a fair amount , its always worse looking on albinos.

That said do check his paws, that’s really the key to knowing if its a lot or like A&B said, simply him having a discolouration on his nose.
Normally they go away in about a day after grooming.
And if you do notice sneezing do get him to a vet

Chew gets this after rearranging his hay right after drinking water.

Peep does! Localised under nose staining-he gets a yellower shade though . ALWAYS gives me heart failure.
Yumi gets a similar version to Nimbus, and i dunno how they get different shades from the same food.
Do keep an eye on it especially if its not normal, for him.

A lot of the time nose discharge is more ‘whats normal for your bunny’ than what is normal for everyone elses.
Yumi for example gets a wet nose every once in a while, nothing has ever come of it no matter how many vets sampled her

It could be staining from hay dust, and it really shows because of the white fur? Most rabbits have some sort of wetness around the nose because of hay dust, so when I think about rabbits going head into hay, the dust probably sticks around and stains, similar to lettuce staining around the mouth.

Does that sound plausible? It’s good to consider checking paws as well.