Did a little digging on soil ( no pun ) and it is a highly ammended with extra bat guano. Slow release guano .
Plant’s leaf overall look shows dark shiny . Nitro tox. Leaf edges reflect the excess.
Flushing does nothing , since every time you water it releases more nitro. I suspect many this mix is geared for other plants ( leafy greens / long seasonal ) than cannabis. All that excess will hammer the flowering ( nitro tox can result in smaller buds , smaller yield ).
plus , you are adding FF Grow Big ( which is a highly concentrated anyways ). Heat and ph issues will make things much worse.
IMO .... I would stop adding ANYTHING for Feeding. I would water only ( as needed ) so plant can try to burn thru just the elements in the soil alone. Dial ph to 6.5 - 6.6 . No more full blown flushing . Let plant try to work thru it without dumping a hot feed on top of it.
That mix would have to be cut / diluted with a milder potting mix to really be useful, alone it’s way too much.
