Join Date: Jul 2013
Location: Clarksville, TN
Okay, so I did a LOT of research and what I found was generally that you have a couple of choices, since lack of light at the base is probably what's causing the root-level die off:
1) Spread the plants out so that the bases get more light
2) put aquascaping in front of the bases to hide the leaflessbases
3) add a light source behind the tank to increase light to the plant
4) re-cut and replant often.
Some of the forums and articles I visited noted that this plant often grows as a ground cover in swampy areas, but is also fine completely submerged. According to what I read, you also might be over-doing it with the additives a little bit. I have no idea how much other stuff you have in your tank, though.
You're not really doing anything wrong, though. These are just noted problems that often occur. One forum did recommend starting these in a separate tank with only about 2 inches of water, and laying them sideways, to get the roots to develop, then moving those to your larger tank once the side shoot got larger/taller.