If they stopped growing it is probably because they are either under fertilized, over fertilized, under watered, or over watered.
Putting them in soil might fix your problem, but the reason it will fix the problem is because soil is more forgiving, and helps to buffer against under/over watering as well as under/over fertilization.
Personally I would suggest trying to figure out why they aren't growing and fix that problem instead of just moving them. This way you will at least learn something from the process, and know how to prevent or fix it the next time it happens.
But if that's not your thing, go ahead and stick them in soil. It might take a week or two for them to come out of shock, but they will eventually. If you are going to put them in a soil like FoxFarms Ocean Forrest you shouldn't need any nutrients for 2 - 4 weeks.