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From your pictures, the plant is doing fine. Growing through the stresses of a transplant, give it time.

Well you did it correctly, so nothing is wrong. buffering coco? compare to process on cocoforcannabis.com. It takes a couple long 8-hour of soakings. Loose coco should come buffered. if this is soilless, you provide 100% of nutrition, so it's a matter of balance. If this is an ongoing issue, it's about which direction it is trending. necrotic or dead spots won't heal, but chlorosis can reverse. As long as the degredation stoppped and started to reverse, it's just a matter of time.

Looks like nutrient burn. Just lower the feeds and give it time to grow out of it.

The plant is just recovering from prior stress, maybe add some Calmag, 1ml or something. Nothing to worry about.