Nice low hardness plants

[Yenko]

My fish tank has a DGH of 6, and I'd like to keep it that way because of my clown loaches. Some plants aren't doing very well in my tank, especially valisineria piralis and hygrophilia. (I know those are spelt wrong). What plants do well at 6 dgh, with 1.2 watts per gallon (florescent tubes with reflectors).

Also, do valisineria and sagitarius produce allelochemicals that aren't good for each other? I've heard they do.