I have been trying to reduce the algae I have in my 60 gallon aquarium that has been caking to the leaves of my planted staurogyne repens. I have reduced my lighting to only be on for 9hrs per day and I am dosing daily with flourish XL. I have 4 siamese algae eaters, 2 oto cats, 10 mystery/nerite snails. However, algae continuous to expand on the leaves of the plants I have even though most of the aquarium is covered in plants. I have pictures of the algae, if it helps identifying the problem. It appears maybe a very dark green (but almost looks black on the plants), but doesn't quite match blackbeard, green spot, cyanobacteria, or anything else I can find information on.
This looks like black algae. It's usually a very deep dark green almost black color and is common in tanks with live plants and is due to high light and organic waste from your fish and plants. If you want to get rid of it, keep your light off for a few days, do a partial water change and if you're feeding your plants an aquarium plant food, cut back to once a week (if you're already down to once a week or less, cut the amount in half).
Also, adding more of the Siamese or Chinese algae eater, dwarf algae eater, introducing ghost shrimp or an additional otocinclus will help (I don't recommend a pleco/plecostamus because algae isn't the only thing they eat, and past the juvenile stage they eat less algae and more meat and roughage-your plants- in their diet). The ones I mentioned FEAST on this type of algae and won't damage your plants.
Looks like brown algae to me. Just ignore them, unless their growth is too massive. They won't hurt your aquarium. Indeed, they're quite the opposite and show you that things are coming together nicely. They'll disappear on their own over the coming weeks. Some spots might stay, but they shouldn't increase in size again.
If you've got any bladder snails (got many different names; they're often stowaways on new plants), place some of them on the leaves. At least mines just love those algae covered leaves and they'll just live on them till they're clean again. You can literally watch them eating/clearing "paths"on the leaves, if you're interested in that.