I have a current litter of 5 kittens. They are 6 weeks old. 4 kittens have been eating wet food for over a week but one is still not interested even if I put some in his mouth. How long should I wait to take him to the vet to see if there is something wrong? He is nursing and maybe just a few ounces smaller then the others but definitely not runty. Also my kittens seem healthy active and playful but they all get some small crusties in the corners of their eyes that I wipe out everyday. They aren’t running or goopy and no nasal discharge? Is this something to be concerned about? Thank you.