Has anything like shade, moisture, or neighboring plants changed? I have pink ladies slippers, and I've divided them early on when the first leaves show. I leave as much of the soil intact as possible, they seem soooo delicate! They haven't really reproduced themselves, they seem to take a long time to re-establish, and seem really fussy about where you put them. My best bet would be to mimic the original growing area as closely as possible, and keep them moist. Maybe you could add more soil/compost as a top dressing? Are they maybe depleting what they have? If you could keep them in the same spot and just give them more "food", as in natural soil/compost, I'm guessing natural loam, to avoid moving them unless really neccessary, try that first. I wish I could offer more!

I was concerned about possibly mis-informing you, so I found this link! The info's really good, and the mention of the fungi needed to be present in the soil is important. Perhaps this is what's needed? Hope this helps!

http://www.illinoiswildflowers.info/woodland/plants/yl_ladyslipper.htm

Woodrose711,
Thank you for the link and the advice! I think I'll try your idea of adding more compost. I think I'll get some soil from my grandmother's woods and put that on them.

I'll check out the link too. Thanks so much!

The disinformation on the need for a soil fungus for mature plants is wrong. Soil fungus play a role with the developing seeds and embryos of Cyps. Mature plants can do quite well without the fungus as is proven by the very successful cultivation and propagation of cyps by different companies that grow the plants from seed.
Here is a link to help you in dividing your plant.

Here is a link that might be useful: How to divide your cyp

Thanks for the link on dividing cyps. I will check it out right now.

Do you mean even the pink ones don't need the soil fungus as adults? I've never been able to grow them. My grandmother gave me some of those too. They lived a couple of years and then just disappeared.

That is right. The success of germinating seeds and embryos has been tied to a relationship where a particular fungus invades the cells of the infant orchid plant. But once the plant begins to leaf out and is able to photosynthesize on its own the presence of the fungus is only incidental if any fungal cells persist within the body of the orchid plant.
For acaule check the link. Almost no one grows C. acaule successfully beyond three years.

Here is a link that might be useful: Growing Cyp acaule

Well, that is interesting! I'm going to try dividing my yellow ones later. It sounds like from the article that they are getting smaller because they've not been divided. I sure hope it works!!

Thanks for the tips.