I'll try and keep it short, POSITIVES!
coral substrate, increased CaCO3/ gh. Good for invertebrates like snails and shrimp, there shells are predominantly Ca.
Your plants look like money wort and a stem of water wisteria, some consider "hard-water" plants because they can better assimilate Carbon in the form of CaCO3. The Walstad method makes mention of plants ability to use alternate forms of carbon. I'd go with snails, more water changes and a whole lot more plant mass, try sag subulata. floating plants are also cool in the aspect that they remove nutrients from the water but get there co2 from the air. good luck!