30 gal recirculating top fed dwc . 3 18 gallon totes 1 for res other 2 1 plant each . 4 weeks in flower gh flora trio hydra guard and calimagic. After water change hard to stabilize ph takes me 3 or 4 days to keep it the same . Say I check in the morning make my adjustment then check in afternoon and I'm good . Next morning low . After a few days gets evened out. Then when I change over again . What am I doing wrong.