It's getting too much light. You'll have to block it.
I've struggled to grow immersed plants (gravel/sand substrate), especially while battling the algae, which smothered some of my efforts. Anubia is hanging in there. Noticed the guppy grass is growing. Hornwort and duckweed are super. Just added some potted Pogestemon octopus and Hygrophilia angustifolia.how's other plants in your tank doing?
Many fertilizers use iron EDTA. It is only usable if the PH is below .6.5. If you PH is above that the iron would be unavailable for plants.I've been working on bringing down the pH, which may have been part of the problem for the plants.