Why? When you switch to flower , you cut back npk, and start the bloom fem fertilizer regiment, but what I do is cut the npk to half and start my bloom at a 1/4 strength for every feed, gradually over 3 weeks taper towards the bloom while cutting npk. I water heavy these weeks to get a semi flush going till I’m at 100-% bloom fert.
But once fully transitioned to bloom I add back 1/8 the amount of npk with bloom every feeding through up till the last 2 weeks when I taper off all feeding and water only to prepare for chop,(like a flush period).
Your plants look overwatered. And starving