I had the same problem in my nano tank - didn't exactly look like hair grass, but more of an engulfing could. Excel, CO2 and lowering of lighting did not help and the plants eventually died.
On my second go around with my tank, the same problem occured and I've since dropped in an amano shrimp and added some frogbit at the same time (heard floaters are almost necessary for tank health). The problem seemed to have been solved almost overnight!
*Edit - seems like you already have some amanos in there. If you are feeding them, maybe you can limit it so that they feast on that algae.