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It could be the start of black beard algae or more likely filamentous algae.
Having lots of plants to use the light can help reduce algae problems, or reduce the light a little bit. A small suckermouth catfish or mystery snail might help too but if the filaments get too big they won't touch it.
I wouldn't turn the light off. Maybe reduce the lighting period by an hour each day and see how they look over the next 2 weeks.
If you post a picture showing the entire tank and the battered plants, we might be able to identify problems with them.
The sword plant leaves are dying because the plant was grown out of water (which is normal for that type of plant) and is now underwater. The plant will draw the nutrients out of the emersed leaves and use them to grow new submersed leaves. Just leave them until they are brown and the stem starts to break down, then use a pr of scissors to cut the dead leaf off and remove it from the tank.
The plant with leaves that looked a bit tattered on the ends looks like someone is eating it.
The last plant is a Java Fern and the little thing on the end of the leaf looks like a baby plant. Just leave it on the parent until it is at least 3 inches long or it comes off the leaf by itself, then attach it to some driftwood or a rock.
Never get a fish to do an aquarists’ job. So called “algae eating” fish are wonderful fish to keep, but will not keep your tank clean for you. In fact, they actually need a tank with plenty of algae or they will starve.
To be clear, I’m not trying to imply any failing on your part. Your tank is already cleaner than most! For reference, my “hair algae issues” entail green hair across the entire substrate if I neglect to gravel vac and manually pull it out. I wouldn’t call what you have “issues” at all. You have “minute evidence that hair algae exists in your tank.”
Siamese algae eaters should be kept in groups in a tank way bigger than 10 gallons, I'm afraid. Recommended minimum tank footprint is 150 x 45 cm.Hubby and I have been talking about getting a 10 gallon. Maybe once we get that set up I could move the cherry barbs into there and then possibly consider getting the Siamese algae eaters for this one.