Green spot algae reacts pretty quickly to an increase in PO4 - that stops its growth. If you have just a few splotches of it, just increase the PO4 you dose by 50% or so and it should go away. But, if the glass is covered with it, you will probably have to scrub or scrape it off first.
I don't know how big your tank is, but if it is over 20 gallons you have a high light intensity, so it would help to get things under control if you could drop the lighting intensity. Make sure you have good water circulation in the tank, so fertilized water is being supplied to all of the areas of the tank. And, at the risk of being a broken record - start raising the CO2 bubble rate a little at a time. That, plus mechanically removing as much of the algae as you can, should get it under control.