Yellow leaves in one week: Week 9 auto

Hey Growmie, There are definitely some things going on here that aren't due to the normal fade most plants experience nearing harvest, now as far as correction, it's going to be pointless at this time because the plant is close to being done. I would go ahead with a flush and go ahead and let them finish up that way. Feel free to shoot me a holler if you ever need any help, I'd be honored to assist you. Hopefully, this was helpful, and remember ... "Happy Growing" and "Free your mind one puff at a time".

The plant at front right is suffering with burning from an excess of nutrient salts in the plants substrate, otherwise known as nutrient salt toxicity, caused by feeding too much and too often and without adequate run off each irrigation. The plant at the back needs more P/K though and the one at front left is suffering with a cal/mag deficiency. Each plant has its own nutritional requirements and feeding every plant the same thing does not necessarily work, as is the case here. In future you will have to "tune in" to each plant and learn to identify that plant "A" needs more feeding than plant "B" and plants "C, D and E" are somewhere in between (for example). It is too late to fix anything much with this grow, however if you had asked this question 3 weeks ago when these symptoms first became apparent, then there would have been time to solve this riddle.