Your Phosphate is way high. With zero Nitrates and measurable Phosphates (anything above 0 on your test kit) you are asking for trouble. 2 is high, 5 is way, way high!
The opposite is ok - you can have zero Phosphate and 10-20 (or even more) Nitrate and have no problems...
Here are 4 steps that will make a difference for sure. Basically you will be "resetting" the water parameters (especially Phosphate) and starting with a clean tank:
1. Eliminate the Phosphates:
Do several small water changes (5-10%) every day in the course of a week. Of course test your tap water - it may contain Phosphates
Reduce the fish feedings to a small one every 2 days.
Every time you change water manually remove as many algae as you can.
After that week of water changes and reduced feedings you could test for Phosphates. Keep in mind that even your test kit shows zero there still maybe enough Phosphates to cause algae. But to make things simple just bring the Phosphates to zero on your test kit.
2. Add enough CO2:
After eliminating the Phosphates take care of the CO2. Diffusing the CO2 with a airstone may seem efficient but it is not. For a 75 gal. tank 1 bubble per second of CO2 should be a good amount to pump, providing you diffuse the CO2 well. In your case the easiest way to increase the efficiency of the CO2 diffusion is to place the airstone under a powerhead. The bubbles will get sucked by the powerhead. They will come out of it like a cloud of tiny bubbles. Let them float all over the tank - that seems to be the best way to supply CO2 to the plants. If you don't like the looks of bubbles floating all over direct the flow of the powerhead along the back glass or find a way to conceal it.
Do not try to lower your pH by pumping CO2. It's better to just make sure you pump a lot of CO2. 1 bubble per second, airstone, and a powerhead is a good amount, but can be increased if the plants still don't grow.
3. Calcium and Magnesium:
The increased CO2 by itself should make a difference in the plant growth. No need to add any fertilizers. But if you see no change check the Calcium and Magnesium of your water. Plants must have both of them to grow. The Calcium should be roughly 4 times the amount of Magnesium.
4. Fertilizing with N, P, K, Fe/Traces:
Only after you have the CO2 right, the Calcium and Magnesium figured out, and no readable Phosphates and Nitrates you can start carefully adding Nitrates, Phosphates, Iron and Traces. Fertilizing a nicely lit tank like yours with not enough CO2, Calcium and Magnesium is pointless and it only causes problems, so get them right first as I explained above.