Good Background Plants for 6.2 Ph, 84f, KH 3 Discus Tnak

Any help appreciated folks. I've tried Camoba, (too warm?).
Sagittaria, Vallisneria, (Giant)Hirgrass, and a couple of others. They just
wither away after about a week, turning brown and mushy. I have great luck
with ludwiga, crypts and some plant called and 'onion plant' which I think
was misnamed. (Also with Dwarf Hairgrass which took over the front of my
tank.) My lighting is 10 hrs of 2.3/gal (55 gal Tank) and I give it a
blast of 4.7/gal for about and hour or two once a day or so. 6 3" Discus,
5 Otos, 10 tetras 3 Cordys. I supplement wit CO2 about 1-2 bubbles a sec,
use Trace Potassium, Iron, Flourish. Nitrates are stable around 10 to just
below 20 ppm. 3X week 30 to 50 % water changes.

My only thought is that perhaps I'm planting them too far back against
the tank and perhaps the light can't reach them as much as the
middle/foreground?

Thanks for any tips.


Jim C.