I wouldn't worry! Obviously he needs something in them, and really like thems. See my earlier post on "Momma, I looooove your brocollis!" It'll be back to chicken nuggets & hotdogs before you know it, lol!
Besides, they're so small, 3 clementines must equal like only one small orange. DS1 has been known to eat 4 apples in one day. I'm not compaining! As long as he's not getting a bunch of other sugar, you should be fine.