Mg deficiency?

Not magnesium deficiency, but ovwe fed, burned and possibly the wrong pH. Haze type strains can usually get by just fine on half strength nutrients, this goes for strains with heavy Sativa genetics too, anything with 70% or more sativa genes. 16 weeks is a long time.

doesn't look like Mg.. .it'd have spots along with interveinal chlorosis. when your plant is all stretched out, there is no reason to defoliate. It is not high-risk of any problem and light hitting a lower leaf is less effective than hitting a leaf closer to the light. Removing leaves can also exacerbate the excess stretching that you have. maybe one of the magical products you useed? it seems to have come on within 1 week with very fast progression, if your diary info is accurate. Do you use a foliar spray? not all plants have teh same sensitivities. Oddballs do exist and could have damaged it that way doing something that is not necessary in the first place. do less.. let the plant do its thing. nutes... if really feeding at 3.6 EC You might be lockingn something out. The ratio of nutes is equally important to overall concentration of nutes... soil has a bunch of unknowns so it is more difficult to diagnose with high accuracy. if using ssoil nutes, a 2-1-2 weighted average ratio of npk and 4-2-1 of K-Ca-Mg will do you good.. if using soiless nutes the NPK ratio should be 1-1-2. You need higher proportion of N with 'soil' nutes because N is not readily avaialbe without bacteria breaking it down.. it won't diffuse into plant until the bacteria breaks it down. soilless/hydro nutes are different in that aspect. after that, fine-tune overall concentration based on observing the plant's resulting growth. Not enough info given to figure it all out. not reseasrchign all your products used etc.. that's on you. foliar sprays are useful tools for specific contexts. Using them when there is no need amounts to masturbation. they can provide immediately local relief for 'some" nutrient issues. Not all nutes can traverse the stomata. You can clog stomata doing this too often... Carbon is gained through the stomata, so clogging them is a very, very bad thing. Carbon is your limiting factor.. it needs to be maximized not clogged. roots are for nutes.. if you have to foliar spray to mitigate a nutrient issue, you need to also reformulate your nutes to avoid this problem the next time. it is avoidable. it is not necessary to feed a plant through it's stomata... that's incredibly inefficient and incomplete way to do things. use a foliar spray for a sepcific reason.. not because it makes you feel like you are improving your plant through action that has little to no effect than simply doing it right in the first place.

To clarify what BerrySweetHigh said about my answer, i said the following ‘I'd go down to 1.8EC max’ Meaning maximum concentration, not a minimum. You can 100% feed below this amount. Sorry for any mixup. Lots of good advice below from everyone, device a plan that works for you. Good Luck!

Overfertilisation should be illegal! Why do you ask, if you have a deficency? What is wrong with you?

Hello my friend, AsNoriu is right! With growing weed you need a EC and pH within the right range. m0use did advice to give EC 1.8 but that is still waaay too high for a plant in this phase giving around EC 1.4 is more then enough! And during this phase a pH 6.2 is better. You need to do a heavy flush!!! Give 4 times the pot volume in water. So if you use a 10 liters pot then you give 40 liters with water. Because your EC is so high you want to give only water without nutrients with pH 6.2 Let all the water drain away, put the plant back and let the soil dry. You want the top inch from the soil to be completely dry before watering again. When the soil is dry you can start feeding EC 1.4 and pH 6.2 During flowering you increase the EC to 1.6 and the pH to 6.5 Goodluck buddy! 💚

Burn or heavily low ph and loads of food, aka burn. Nothing else i would say.