My 55 gal tank parameters are very similar to yours (exact same KH/GH, my PH is 6.2 with CO2 saturation). I noticed some minor deficiencies in my plants and made some fert adjustments about two months ago with great success. The biggest changes were adding more K & micros and different types of Fe. Here's my advice, for what it's worth:
I think your dosing schedule is fine and shouldn't be changed. I also think your 50% weekly water change is good. Your phosphate level looks good, too.
Your nitrate is a little low. The test kits aren't super accurate, so if the true value is lower than your test, you may have very little NO3. That will definitely create problems. I would dose enough NO3 to keep your water in the 20-30 ppm range. I prefer the Salifert NO3 test kit. It seems to be fairly accurate and has a good color range that's easy to decipher.
Your K might be low, too. I would add some K2SO4. I don't need to dose much NO3 due to bioload, so I'm currently dosing 1 tsp K2SO4 on my macro days. I know it's more than enough, and excess won't hurt anything.
I did a lot of research on iron and determined I was likely deficient, so hopefully this brief explanation will save you some time. I'm not sure what trace mix you're using, but it may not have the type of iron, or enough of it, that you need. You mentioned Seachem iron, which is ferrous iron gluconate. Plants will slurp that up because it's the easiest for them to absorb based on its chemical composition. However, it doesn't last long in the water and will probably be unavailable after a few hours. I recommend dry dosing Plantex CSM+B, DTPA Fe 11%, and iron gluconate. There are different chelates for iron ferts. CSM+B is a really good micro mix, but its iron is EDTA chelate. EDTA chelated iron becomes less available to plants as PH increases above 6.0, but it lasts longer in the water than iron gluconate. DTPA is another chelate. The plants work harder to get the iron from DTPA, but it remains available at high PH values and lasts for days in the water. I briefly dosed dry iron gluconate, but my UV sterilizer caused it to precipitate and cloud my water, so now I just dose CSM+B and DTPA Fe. If the UV sterilizer cloudiness is not an issue for you, I recommend dosing all three. Like any of the other ferts, it's way cheaper to buy dry iron gluconate instead of paying for Seachem's water mix. I increased my CSM+B dose to 1/4 tsp on my micro days, and now also dose 1/8 tsp DTPA Fe. I don't test for iron, but I use this calculator (https://rotalabutterfly.com/nutrient-calculator.php
) to target roughly 0.5-0.6 ppm total Fe. It's not exact, but if you dose all three types, you get the best of all three regarding ease of absorption and availability to plants.
I bought my dry ferrous iron gluconate here: https://aquariumfertilizer.com/
I buy my CSM+B and DTPA 11% iron chelate here: Aquarium Plant Fertilizer | Green Leaf Aquariums
I've noticed big improvements in my plants, both in new growth and in growth I now consider old since increasing my ferts. Hope this helps you.