Lee...you should have no problems with vallisenara by cutting it...firstly if you cut it with scissors it looks too groomed...try pinching them out with your hands..the uneven cuts make it look more natural. Dont give up on these guys just yet...it is very common for them to die off at first, alot of plants will do this..and then re-appear...some as late as a year later. In the meantime..just continue what your doing..if your are growing to the point that you need to cut them...you have your balance right for this plant. Wait a month or two to see if they bounce back (then ones that died) im sure they will
Cabomba is another one yes..but it actually falls into the classification of an expert plant. Cabomba is so readily available that most ppl fall into its trap. If it reaches for the light and becomes to stringy then the requirements are not matched. This plant should be tall and bushy. You can however trim and replant..but it will not last that long..actually...the taller it grow..if fast...the less the requirements are met..if that makes sense. I have several reds and they are extremely hard to keep..and expensive..try the dark green variety first...other plants to look at are swords...and java ferns...java moss, anubius...just dont burry the roots