Leaf Discolouration in Flowering

Yeah, like GM said below - if you are dosing to prevent / counter what does look like a mag deficiency so it soubds like you are doing the right thing, but if it is getting worse there are a few things to think on: What pH is your substrate? Is it in a good spot? pH & ec your runoff - if your pH or ppm / ec is sky high you may have spotted the culprit. That is not a small plant, you are also well into flowering now so they will be getting hungry - are you feeding enough? They are gonna be burning through nutrients now to push big flowers. Are you getting any red / purple on your stems? Are you adding enough epsom salt to your waterings? It could be Sulfur def (looking at diary pics) as this commonly starts yellowong on mid section leafs but your epsom salts should stop it spreading with the right dose too. An often overlooked nutrient as it can look like N deficiency when it progresses and when it comes alongside an N def it could be very difficult to diagnose. It could also be early stages of potassium - comes in mid to lower portion, affects leaf edges, starts yellowing and gradually turns necrotic (browns off on the edges). You can make a banana peel tea for Potassium deficiency. Potassium lockout can be caused by too much calcium present in substrate. A few suggestions to go on for you, it is a big plant with a lot of leafs, it is common to get the odd yellow leaf on a healthy plant, especially as you progress through flower. Stick with the epsom salts when you see the need and maybe try upping your feeds and working some extra potassium in - but bear in mind that too much mag can cause a block on your cal if there is enough mag available in your soil, too much cal can block potassium and too many nutes in general can cause burns😅 Hope that helps.