hey man looks like they are struggling with the PH fluctuations, this is the hardest part for this though, nothing much you can do except add less PH down, if I were you though i would add some cal mag at least if not other micronutrients as well, another thing that may help is using the correct chelation agent, for example a 5/12 humic fluvik acid mix. I hope this helps my friend ! 🚀