Regarding the Algae...Some types of Algae will not rub off but it only works for some types. Black is particularly tough!
How long are the lights on during the day? That is the usual culprit. I would cut back the photoperiod if the lights are on longer than 8-10 hours. Also I notice you are using an Actinic 50/50 light. Actinics dont do much for plants and IMO opinion you would be better off with a daylight lamp. 6500K-10000K depending on what look you like best.
Are you fertilizing? Over fertilizing would also potentially cause algae if the plant uptake of nutrients wasn't able to use up what is added.
This is where Co2 comes in...plants need nutrients,light, and Co2 to grow. When one of these things is decreased the need for the others need to decrease also. When one is increased the others need to be increased as well. (With me still? lol)
So less light requires less ferts and Co2. More light requires more Co2 and ferts. You get the idea.Plants adapt very slowly to changes in any of these parameters. When one of these is off it allows Algae (which is much quicker to adapt to change than plants) to have the nutrient intake advantage and thus gain a foothold.
Long story short, Co2 is a big factor in giving plants the advantage they need when it comes to growth and nutrient intake. I think you would likely benefit from some form of Carbon be it through a pressurized Co2,
DIY Co2, or Flourish Excel. IMO the Excel would be the best bet in your case.
My 2 cents, hope it helps.
Nate-