Thank you for posting that Aquaticlife manual. I added the PAR data to Lighting an Aquarium with PAR instead of Watts
along with one of your photos of the reflectors.
You can see, from that chart, that at 33" you are getting about 70 micromols of PAR, which is more than enough light to grow hairgrass. If you were to use just an adjacent pair of bulbs you would get about half of that, or 35 micromols, which might be too little light. But, lower the light to about 22-24 inches from the substrate and you should have about 45-50 micromols of PAR at the substrate from the two bulbs. That is plenty of light for hairgrass, and based on the charts in the manual, the light would be adequately uniform over the whole substrate.
I suspect your problem is a CO2 problem. Once you have enough light, and dose fertilizers per an EI method, 90% of the problems you will run into are CO2 problems. I suggest:
1. Make sure you have good water surface ripple over the whole surface. No splashing, but good rippling. This keeps the water oxygenated so the fish can live with high CO2.
2. Make sure you have very good water circulation in the tank, with all leaves on all plants swaying in the current. This gets CO2 rich water to all plants.
3. Increase the CO2 bubble rate just a tiny bit. Watch the fish for distress, and the plants, looking for improvements in their health and growth rate. If the fish aren't distressed, repeat this step about every 3-5 days, until the fish aren't happy - then drop the rate to the last one where they were "happy". Or, repeat until the plants are growing in obvious good health and at a good rate. It may take a week at each bubble rate to do this well.
If you want to do a "noon burst" go ahead, but I think it is better to eliminate that while adjusting the CO2 to an optimum bubble rate.