Is it a magnesium deficiency

It appears to be a combination of buildup and acidic soil medium (4.8 ph) i've flushed and feed her after checking the EC.

Thank you all for your responses, Got an EC meter and saw there was a serious buildup of nuts and also very low PH readings. I have flushed here and managed to balance her EC. (Reduced the amount of nuts in half) Lets see

Looks like nute burn. Maybe that pheno can't take a big feed. Can probably just be mindful and just use water for a week.

Give it some cal-mag and something with like 2-4% nitrogen.

Hi, you literally toasted your Girls. the way they are growing with short internodes, says me, your light is to strong/ to close to the plant these are lightburns happened 2-3 weeks ago and still continue. plant will look more bad. because the yellow parts get brown and leaves yellow and crispy immediately dimm bak your light to the half power you use now, or double the distance. new grow should look fine if you do that

As Steve said, Potassium deficiency also shows yellowing leaves, burnt tips and droopy leaves at the top. Your plant is showing all the signs as well.. I believe Steve nailed it and I didn't. Regardless I would check runoff and see where your EC or PPMS are and your PH. This will tell you exactly what's happening down there.

Nah bro you got to much. Your experiencing lockout. Check your runoff wyaer with a ppm or ec meter. This will tell you how much buildup you got. From the looks its a toxicity not a deficiency. Due to the fact its top leaves not bottom leaves. Deficiency starts from bottom up. Toxicity starts at the top. Your ph could be out of wack too. So check that in your runoff. To fix this I would flush with 2 or 3x the container size in water that is PHd correctly. Then I would check the runoff and only stop when the ppms are where you wanted them or right below your input ppms when you feed. Once done flushing follow it with half a gallon of half strength feeding so they have fresh nutes. I would also suggest using RECHARGE. it will help prevent this. It gives all the good stuff your roots need. Microbes and fungi and bacteria but the good kind. They help break down nutes and feed them to the roots. Helping prevent lockout. Use it once weekly or once every 10 days. Goodluck growmie. Please consider selecting me as the answer so I can be entered for a chance to win grower of the month contest I would really appreciate your support growmie 🙏 😃

Man, from the looks of your plant you have a bunch of shit going haywire. I see nutrient burn, over watering, magnesium deficiency, likely calcium as well. You need to FLUSH that soil with clean 6.2 pH water. Then allow the pot to get light when you lift it. Then water in a balanced nutrient mix with a 6.2 pH Thats what i would do if it was my plant.

potassium deficiency