Most of these issues evolve around light and organics. The more light the less organics the tank can deal with. The best way to get rid of it is to work on both ends of the problem.
Reduce light duration down from the 8 hrs to 5 or so. Increase water changes and use Purigen and/or Carbon in the filter. If the plants don't look like they are healthy then also add more fertilizer if your only dosing Seachem Comp.
I would also just cut off affected areas. if the tank has what it needs they will grow back, if not then something is missing in way of nutrients.
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