Welcome back emvanburen!
I run the hydras just on the standard Red Sea Reef spec (as per instructions)for most of the day and then change to mainly blue around 7pm as the lights ramp down. Just because I like it that way.
On the NoPox, what you are experiencing with phosphate and GHA is exactly what happened to me and if you read my build thread you will see. Nitrates were perfect at your levels but phosphate just keep going up and up, GHA broke out and when phosphate hit 0.16ppm that was it. Installed Rhowaphos with Deltec FR509 reactor and never looked back. Phosphate is locked down at 0-0.03ppm and it's the best thing I ever did for my tank keeping phosphate down.
I know what Red Sea say about NoPox and the use of other products, but my nitrates have gradually reduced from 12-16ppm (everything was very happy by the way) by using other products in addition. I had to look into other products because it simply would not keep phosphate in check and nitrates were rising.
I currently run NoPox at 14ml per day (my Nitrate is currently around 6ppm but I'm happy at this level and will slowly drop the dose down a bit as only just getting to these levels), I have a Seachem 'The Bag' with 250g of Purigen in the sump, and I also have 2 x Brightwell NO3 Xport bricks, and of course Rhowaphos, activated carbon, and in my case the combination has everything locked down. Well at the moment anyway!
I would love to just use NoPox on its own, and would recommend it to anyone, but in my case probably due to the high bioload I needed something in addition.
And if your wondering how I beat the GHA. After adding the Rhowaphos the GHA very slowly started to die back but there was some stubborn GHA that wouldn't. So after months of frustration I added Vibrant and dosed it for just 2 doses over 4 weeks and it disappeared totally. I lost 2 Elegance corals that reacted badly immediately after dosing Vibrant but the GHA was gone, never to be seen again.