[mistergreen]

How often do you change your water?
remove the affected leaves. They’re dying and leaking nutrients so algae grow on them. Looks like staghorn.
25% water change 2x a week seems to help a lot.

 

[mistergreen]

Any leaves with holes in them are damaged. Simply prune. People forget a gardener's job is to grow and prune.
Water changes remove waste nutrients and replenish Ca, Mg, and some other micronutrients.

 

[mistergreen]

yes, prune leaves covered in black stuff too. That could be black beard.

 

[mistergreen]

Oh, try turning down the light duration too to 7 hours. Too much without co2 is no bueno.

 

[mistergreen]

Keep adding ferts. Plants need to eat. Reduce your light duration.