New growth and top leaves have some discoloration. Could it be light related, or maybe a zinc deficiency?

it really depends on too many factors to give a certain answer. you need to know what's going in. i see you already got tons of data... now convert that nutes spreadsheet to ppm -- only because it's commonly used. Molarity would be a more common sense measurement, but ... not everyone takes 3 or 4 semesters of chemistry just for fun as electives. now, i'd reference some various formulas online.. i can;t recall the forum, think it was rollitup?, but it listed a bunch of companies and had it all worke dout.. anyway just for baselines and references to get us in the ballpark (am at same stage). Now, with that info, you can make a super smart decisions as to what was available.. and if it was, then you know it's lockout to due overabundance or whatever else or some other environmental/microbial variable wreaking havoc. if zinc is readily available, you can eliminate that. it does show those symtptoms, but a few others match it too. If you increase photosynthesis, the plant will need more nutes. so, that could also be a big factor here.. you ahve all the info, which is f'ing awesome, love it!

Give 1 ml/l cal mag, it is a deficiency of the 2 due to the higher speed of photosynthesis.

You know you have to mix in your micro last, right?

I would say that is a little week at this stage. I'm not saying you go this high, this is my feed. I start babies at 300 ppm 0.6ec, then the next week 400 ppm 0.8ec, to 500 1.0ec ppm with no I'll effects. Then 600ppm 1.2ec, then 700, then 800, and finally 900 when I switch to 12/12, once they start to bud, about 2 weeks, I back them off to 600 ppm cuz flower ferts are stronger and can now burn your plants. About the 5th week into flower I increase ec to 1.5 800 ppm. I would say your safe to runmyou girls at 1.2ec 600 ppm. I am not an expert at coco but it seems your girls wanted a little more food. Coco is a form of hydroponics. I run max lighting and perfect environment so you can't go the limits I just said. Do a little more trolling for how successful coco growers feed. Happy growing my friend

@gmslave it is 70/30 Coco coir/perlite. And currently I am feeding at 1050-1150 EC. Following the nute schedule from cocoforcannabis.com. I will add a pic of the schedule to week 4 of my diary with the phase I am on highlighted (early flower). Currently well into week 5 but I usually update on tuesdays for the whole week.

What type of lighting are you using as well?

Is it coco or peat base medium? What's your total ec your feeding?

I'll rule out light burn. Not sure what it could be. Diary looks good. Sorry man ☹️.