Its hard to tell in the pic but the algae looks like it could be pretty bad. Plants have it and maybe on the substrate too
Its not related to nutrient levels (saltwater is different) its there because the plants arent happy. And since its there now you have to do two things: Remove the algae and get the plants happy
What I would do
Manually remove all you can, including vacuuming it off the sub, even if some sub goes with it. Remove any crappy older growth that is deteriorating and replant the best part of the tops
After doing that Id probably use peroxide or excel. Turn the current off and spray the crap out of everything under water. Let things sit for about 30 minutes, then do a big water change. With peroxide you can use up to about 3 oz. With excel 1.5-2 ML per gallon. Thats with the tank full of water. Dont use excel if you have Vals, it'll kill them
Couple days later any leftover hair algae will turn white and disintegrate. Ive used this method many times
You may not need the chemicals, like I said cant tell how bad it really is. An aggressive clean and prune may do the trick
Next thing is get the plants happy
With inert sub for macros I'd dose 15-20 NO3, 4-5 PO4, 25-30 K per week with 50-60% water changes. With bigger water changes Id raise it 25% or so
Micros at .4-.5
ppm Fe per week regardless of wc volume, split 3x