The only thing i can think of is the perlite/verm. is holding on to more nutes than waterThat's a good way to put it. I've resolved not to chase it, but it's hard to ignore. i just wish i understood the chemistry going on that so quickly dumps what when in at 5.5 out at 7+.
Not sure its nute burn mate. Kinda looks like a ph fluctuation problem? Im far from an expert though. You could post in the live help thread for some expert advice. Keep us updated mate