Nodes 4 and 5 are really close together at the top, great time to FIM or top imo. As for the yellowing cute one, I would hit it with a bit of kelp foliar, or basic tea, to up its' local microorganisms .. the outside of the pots may dry faster so just watch out for that. The canna trim, albeit very cool looking, may take too long to provide what you're really after, although on second though, N def's start from the bottom up, not top down. If you can add a little bit of nice weak white light, higher kelvin, that may help nurse her back too. Clean set up by the way, keep it up!