When you bloom, your bottom leaves usually turn yellow, and the yellowing in the leafs may have been caused by over nuteing..dude i went with all light mix at last grow.tried to follow the feeding schedule ı did before.using hesi not biobizz.(not much choice here)its ok when growing but i had issues when blooming start.lots of yellowing bottom leaves and gave them a lot more nutes.it looked like me kinda waste of nutes.glad you have good results