How long have you had the rock with them on for?
Where did the rock come from, Indonesia, Australia, New Guinea, Caribbean? You might have to contact the shop you got it from to find out where it came from.
There is a book called "Field Guide to Anemonefish Fishes and Their Host Aneomes by Daphne Fautin & Gerald Allen. It is worth getting if you have Anemones. Below is a link to the contents and you might be able to id them from the info at the website. http://jjgeisler.com/reeftank/anemones/
The could be young bubbletips (Entacmaea quadricolor) or one of the small colony anemones. Give them lots of light and a bit of marine food a couple of times a week and see how they look in a few months.
The book does not cover all anemones of the world but it does cover the anemones that are used by anemonefish. If they aren't in the book then google colonial anemones.