m0useanswered grow question 6 months ago Potassium normally starts on the serrated edges of leaves not in the leaf itself. and it is not normally spotty like that.
I think you initial assessment of Ca is correct, it will take time to recover but should stop progressing, The existing damage will not repair.
https://420life.com/wp-content/uploads/2021/10/Marijuana-Leaf-Deficiency-Chart-scaled.jpg
This chart can help.
Good Luck!