What is causing PK deficiency signs on mid leaves? Too little Calcium causing lockout??

Sometimes deficiencies happen due to ph lockout. You should check the ph of your soil (slurry test) and the ph of your water. Thats what helped me with my current grow.

Looks like you had a strong nitrogen toxicity, but you dialed that back. Coco tends to hold a lot of residual calmag also. My suggestion is to drop the micro and calmag for the next few feeds and see how she responds. If the coco is holding a lot of residual salts, it may continue to get worse for a few days before the spread stops. Make sure you're testing the pH and EC in the runoff as well. A high EC in your runoff would indicate that the medium was too hot and pulling back the micro and calmag is the right move. Good luck!

Ive just uploaded the deficiency pics to my diary week 11

For more info, I reduced the calmag a while ago to reduce the Nitrogen as Vitalink calmag has 1.8 N. The coco wasn’t buffered (first grow mistake) so should I maybe do a calmag watering first with each nute mix?