Well, in Bow tanks and corner tanks it is extremely difficult to solve the riddle of flow/distribution. Because of the awkward geometry it's difficult to guide the water to all the locations evenly.
Your photographs are more intended to show the tank contents, but really, it would be more useful to show exactly how you are distributing flow and what the placement scheme of your various pumps and filter outlets is.
It looks to me from photo #2 that you have a powerhead pointing from the front of the tank to the rear left, which is the worst possible angle because that is the longest distance between any two points on the same plane in the tank. The flow spreads out in a conical shape and the energy is disipated everywhere, which essentially means it goes nowhere. I can see that the Vallis-type plants are bending over to the left, possibly from that powerhead. The plants located under the powerhead are not gaining any benefit from that.
I'm not seeing how the flow from the filter is arranged. I'm guessing that it is located somewhere along the top, pointing at a different angle and outside the plane of the powerhead's effluent. If so then there is probably collision, or at least interference of flow and cancellation.
When you add multiple pumps to a system they must work together as a team of horses pulling the cart along the same plane and in the same direction. From what little I can see of the photo it appears to be in chaos.
As usual, the powerhead should be moved to one of the back walls, preferably alongside the filter outlet tube and pointing in the same direction, preferably towards the front bowed glass.
As mentioned by other posters, KNO3 is the best nutrient addition to avoid nitrogen deficiency, so you ought to be adding that.
I cannot analyze further without more detailed images.
Cheers,
