Could be many reasons.
Low kh can cause problems.
Something with your saltwater, joys of using seawater, did not a sewer line break sometime ago around Wellington?
Too much po4 remover or carbon, probably the problem.
salinity 1.026?? How do you test this? Maybe get it down a bit.
Get your kh up a bit and turn off the carbon and po4 .
Reduce your halides by a couple of hours.
Don’t add anything.
Wait and see