What's wrong with my ruffle sword?

[Meclizine]

I've had this plant since July of this year. I gave it a root tab within a month of planting it and it has been doing well until now. I dose liquid fertilizers (Flourish comprehensive and trace) and I don't have a CO2 system. Around the time the ruffle sword starting looking like that my melon sword did, as well. However, after removing the dying leaf the melon sword hasn't shown any more signs of stress while the ruffle sword has continued to deteriorate. The rest of my plants are doing fairly well (java moss & ferns, dwarf hairgrass, dwarf Sagittaria, Balansae, and Myrio).