Thank you for the reply, we were posting at the same time. I do have some cuttlebone in the tank, I will try the fresh veggies. Glad to hear he is probably okay!The gray on the tip I think is normal, some of mine have that as well. If all of his shell is turning slightly gray he might not be getting enough calcium. Try putting a cuttlebone in the tank and feeding fresh veggies that are high in calcium.
I'm not entirely sure why they change colors, one of my ivory snails turned slightly pink along his back, lol. No idea why. ..