Depending on how much PH fluctuation you got, they may have troubles absorbing P and Mg, if you look at the graphs I added. So maybe try to keep it as much as you can around PH5.8. Starting at 5.4 might be too low if you rePH it too often. I would personally set it at 5.8 or just a bit lower than that and reph it again when needed, so they can absorb all nutes and get healthy faster. So maybe it's more P def than Ca def in your case. Along with Mg def.