keep in mind you can buy t-8 bulbs at home improvement stores, wal mart etc. I dont know what you have for bulbs but just a suggestion. Do a test of your water straight from the tap. Your lfs probably has 10k bulbs because they are bright and maybe make the plants look better but long term they really are not good. Maybe get some root ferts instead of dosing the entire tank for a root feeding plant. Oh ya, cut off that dying growth. Its taking nutes from the rest of the good leaves. They are gonna fall off and they are decaying which could cause spike in params. How long has the sword been in the tank? More times than not the plant will loose its leaves you seen in the store.