This type of alga needs just 3 things to grow quickly.
Light
Water
Nutrients
Of course, all aquariums supply this. Your tests may show zero nutrients but in fact, the alga is using up the nutrients as quickly as you can test for them. This is also why it comes back so quickly after scrapping the glass.
Your lighting period is good, however your LEDs may be turned up too high. Excessive light, combined with just a little bit of nutrients in the water will cause the alga to coat your glass. What are your blue and white settings?
Someone on this forum will probably immediately tell you to get some snails to fix the problem. Although most snails WILL eat this type of alga, they will just leave clean trails on the glass but it will still look ugly and you'll have to manually clean the glass anyway.
How new is your tank? I rarely get this alga on my glass as my tank is established and I pretty much have my nutrients and lighting under control .