DaveGanswered grow question 5 years ago I would suggest it is an nitrogen-defency. Yellow leaves at the bottom is typically shown as nitrogen-defencies.
The defency started already in week 4 with yellow leaves, then you flushed the soil, so all nutrients have been lost compketely, and than you went ahead with bloom-fertilizers only.
You should not completely stop with the grow fertilizers during bloom - I would try to add bio-grow again, with only 50 % dose of usually grow dose, just to give more nitrogen. Hope this will help.