What's happening with ds's teeth?

I was brushing ds1's teeth a couple days ago (he's 28 months) and noticed that both of his upper eye-teeth look like they are (for lack of a better description) shedding, from the bottom up. It looks so bizarre! The teeth are still pointy on the bottom, but it's like the enamel is peeling away or something. Thankfully, you can't tell by just looking at him...you have to be in his mouth to see it.

Has anyone seen or experienced this before? Any idea at all what might be going on?

I'm going to be looking into dental insurance for him before we take him to a dentist, as I'm afraid that it may be a major thing happening. We were going to take him to the dentist around his 3rd birthday, but I guess we'll be going in before then now.

TIA!