
are you feeding at recommended dosage? BB is mild stuff, and if you diluted this all may be a simple lack-of defc.,... It looks like a Mg issue... are you using the whole line-up, or whatever their micronutrient supplement is? Alga-Mic or something like that...? Point is to make sure you're getting the full coverage of nutes beyond N-P-K.....
As for watering, don't let it get that kind of dry, low moisture screws up pH, hurts the roots, stalls out the activity of the soil microbes which you need in good shape using organic nutes like this,... mild cycling is OK, but I don't recommend any kind of dry....
That pH meter, is it made for soil testing specifically? It looks like a regular liquid only type meter,... they are delicate instruments, easily losing calibration and accuracy if not stored right, and kept clean, never let dry,... If it's been abused, it's need calibrating to check it's functions out! ....7.0 test solution,...
That said, it's possible the soil went out of pH range,... best tool for this is a soil pH probe; Accurate 8 is a good unit, much less $$ than the other bulb electrode type "pro" units,....
get the info, and we'll try to decide if that pH reading is to be trusted, this will dictate what's best to do next,.....