Coughing and sneezing is never a good thing in cats and dogs.* It could be an upper respiratory infection and some antibiotics could clear it up.* With cats, if left untreated for too long, it can be difficult to clear up - been there, paid the vet bills for that!* Besides, you have another cat and you sure don't want a senior to catch anything.* If he does stop eating ,that is a really bad sign and needs to go to the vet immediately.
He's gorgeous too!* I'd say take him to the vet today.* Please let me know what you find out.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.