It is next to impossible to tell the intensity of light these day unless you have the data or a way to measure it, which most of us do not have. The "watts" per liter/gallon is useless unless one is using a known entity. I used to use two 40w tubes over my larger tanks, then they became 32 watts but brighter. So we can skip this.
I would reduce the duration. If you had good floating plants, this might be OK. But not here. Most of the time it is the light that is too much (or sometimes too little, but not here). You can twig the duration, I would move it down to 8 hours, then after a couple weeks if the algae is still increasing, another hour.
You probably do need plant fertilizer. You could use a substrate tab, which can work well for swords. Flourish Tabs are very good, the API is not.
The balance of light/nutrients is very important; after I got my tank lighting down to 7 hours, for more than six years I saw no "problem" algae. It doesn't take much though, the increased daylight during summer impacted it, until I solved that problem.
