Nobody is going to be able to tell you if it is Ich for sure. Obviously white spots on a fish are never a "good" thing so I would take the excellent advice previously given and increase feedings and keep stress to a minimum and keep observing. Try garlic to stimulate appetite if needed (but it sounds like it may not - a good thing!).
I would keep hands out of the tank, keep water quality high and feed a smaller amount of nutritious foods 3-4 times per day. No point stressing the fish out by trying to quarantine and medicate when you do not know what the parasite / infection is. A clown given a healthy diet and stress free environment should be able to control ich on its own with its good slime coat. If things go south then consider more extreme actions - at this stage if it is ich no meds are going to be able to kill the parasite while they are under the skin and slimecoat anyway (despite what the med manufacturer will tell you)....imo best strategy for now is feed, leave it alone, and observe.