You might want to make sure the nitrogen cycle is still working. I have done something similar before and I discovered all my cynops, including adults and juveniles, all moved to land. I then discovered that the nitrogen cycle restarted and the water turned poisonous to them.
So, test the water. If things are still fine, then I guess they are just stressed by the change.
If water is bad, frequent water changes to keep water clean and nitrogen cycle going is essential.