Yes a vet trip is the best for peace of mind, especially if the appetite has diminished somewhat, otherwise it could be just a mild cold or allergies, both my kitties appear to have allergies, do you have the kitty vaccinated against cat flue, if not please do so, that can be a killer, but it sure sounds like nothing too serious, but when in doubt, get professional help, good luck and I hope kitty's health improves quickly.