:( Aww. They are great little fish. I love watching their little feelers/pectoral fins. Sometimes they will meet each other and almost look like they are shaking fins. I did lose one the other day though so now I only have a pair.
Good luck.....injecting CO2 is one thing I have never done and most likely never will. The natural CO2 that my systems create is plenty for the species of plants I grow.....but it does limit me on species of plants-but not much.
Sounds like you have most of the low light plants covered....Crypts are great low light plants and some sags and vals will do well in lower light too-but they tend to do better if they can get a bit of natural sunlight.