I just want to point out the significant difference in PPFD readings at various heights.
At 12" the center PPFD readings are over 1000. That is very high and can / will burn plants. The 16 to 18" height is a much better height with higher PPFD readings at the perimeter (i.e. consistent coverage).
What makes miracle-gro tough to grow in is the amount and type of fertilizer it contains. Then, if you add your own it can lead to burn and ph issues.
Do your flush and see what the runoff numbers are. At this point I would put Grow Big away and only use Big Bloom and Tiger Bloom. Big bloom is pretty harmless with its low dose NPK but has other good stuff. Tiger bloom provides what the plant needs to produce better buds.
Next grow look into LST to help manage plant height to achieve more even light distribution over the entire plant. Also find some happy frog or ocean forest mixes.
I think with doing the flush, increasing light height and monitoring nutrient intake, you should finish this grow in good shape. Good luck