Did you uproot the plant and trim the roots?
You shouldn't disturb the roots, and just trim the tops, cutting them down a few inches.
(if I understood that correctly)
Yeah, I was cutting from the bottom, but there were no roots so I thought it would be OK. Roots are being sent out from above the substrate so the plants are getting their nutrients from water column.
I understand you should cut them down a few inches, but this works for me. Plus, since the tank is so small, I don't want the Cabomba overtaking the tank