I agree re those plants and CO2 as well as higher4 light levels. I had 144 watts of power compact fluorescents over the tank, a 50 gal. which is 36 x 18 x 19 inches. I kept a carpet of dwarf hair grass in my pressurized CO2 added tank for a number of years. I also had baby tears in there for even more years. The first pic below you can see both plants. I put both in and let them fight it out. The hair grass won.
This is how massively thick the baby tears in the top terrace above would get. They had recently been given a haircut. Eventually it would raise up like an island showing the roots. I would pull up the entire mass, replant the space with individual strands and throw away about 90-95%. It would be like that again in a few months.
I ran this tank for over a decade. It had a variety of plants over that time as you can see from the pics. My CO2 tank was a 5 lb. and I used a dual gauge regulator and a bubble counter. I got the bottle and guage from a bar/beer supply company. I fed the CO2 into the intake of the Eheim canister on the tank.