I have a similar issue, though in reverse; whatever I'm feeding, it's running off at 5.2, and nothing seems to change this.
I flushed with straight R/O after an eary harvest and delay in processing it for this run due to extremely high ppm runoff... also it was pretty dark. I expected the color to fade with the ppms, but it didn't, and by the time i checked it was too low, and the pH had dropped to 5.2. I flushed with base and
calimagic and some epsom in an effort to rebuffer it, and the runoff ppm didn't change for some time... then it did all at once, and it's a bit too high, but the pH hasn't budged.
Phosphorus is locked out hard, and I'm like a day away from saying fuck it and starting to flush at like 10.0.
Edit: Might have ODed with
Calimagic? I'm seeing other posts which suggest like 1ml/gal, but then later on those same people will quote wholly different numbers, without much reason for the change, while generic terms like "
calmag" are all but meaningless; Jack seemed to suggest 10ml/gal earlier, but does that translate to
Calimagic? Flushing with 2 EC seems ridiculous.