Well, first of all, i don't think people REALLY looked at the plecos that you have in your tank.
First of all, mostly all plecos eat SOME amount of algae in a tank. However for yours, well, the snowball pleco is a carnivore and the royal pleco is a vegetable and wood eating pleco.
So they will eat about 1% - 5% of the total algae growth in your tank.
So next i will look at the most obvious thing to ask and that is with your auto feeders. Are they running every day? If so that is the source of your nutriet problems. If those feeders are running every day that is WAY too much food
IMO.
The fact that it is a new tank doesn't really have much to do with it.
If you are looking for some fish to get that are really small and unintrusive get otocinclus cats. You could also opt to go for a Siamese algae eater (only eats algae and is peaceful).
Let me know the answers to some of my questions to better help you out