I would try crypt wendetii, dwarf water lettuce could be fun I have had success growing that, I have heard around the forum and Girl Talks Fish has a video that mentions Java fern needing a lot of potassium which might have been your issue. I will link the video here with the time stamp
4:16 is the place where she talks about the java fern. I will say the some plants do grow better in some environments then others. Some of my plants have melted away for know apparent reason and I have reordered the same plant over and over and done various things to ensure it survival but it dies.