I've noticed today that one of my baby boys (4 weeks old on Wednesday) has a rather manky lip. He's also got some white residue in the crease behind one of his ears. Looks like another trip to the vet, what could this be? Is there anything I can do in the meantime?
He's eating fine (Burgess pellets, unlimited hay, cucumber, broccoli, celery and little gem lettuce).

He's eating fine (Burgess pellets, unlimited hay, cucumber, broccoli, celery and little gem lettuce).
