I also agree to what Tom and ShadowMac said. When you got the point with a given tank, all plants do thrive in luxurious way. When a plant does bad, often even other plants won't be doing optimally.
But, I also noted that the Downoi stems will stunt when shaded by other plants and slowly degrade from the roots. In very low light, they also tended to grow in the best exposed parts while other dark parts didn't grow. I got rid of it because I find it tricky for my very low light setup. Anubia, weeping moss, eleocharis, java ferns, mini pellia, riccia, glosso, c parvula and even fissidens fontanus all grow well in extremely dark and shaded areas of tank, but with good CO2 (misting)