Brown leaf question

...

Pictures would help. Tank specs too. Are you dosing anything now? Lighting? CO2?
Using Seachem potassium or potassium nitrate are a couple ways to add potassium.

Dual 48" t5ho 6700k bulbs. Parameters are good. Lights cut back to 6 hrs a day due to an algae bloom. I have fert tabs and overdose seachem excel to try and rid the algae. I have new growth in the center of my amazon sword but it's almost like the leaves are white. Some of my plants are doing well like my java fern and golden lloydeillia. Dwarf sag is not producing runners and has been established for a few months now. I really need to get my co2 going but until then I was wondering if potassium supplements with the excel would be enough?