This is a handy chart for figuring out deficiencies although I have found that getting rid of the old food, making sure the PH is right, and putting in new food solves any deficiency I have come across.
EDIT : From the look of the leaves in your image, they are young leaves, with necrosis, interveinal blotches and leaf edge scorching so the chart says calcium.
So now we pull out another chart
You are in soil and if we look at calcium we see that a PH less than about 6.5 leads to lockout of calcium. magnesium, and molybdenum.
This suggests the low PH locked out calcium leading to the deficiency. I would avoid a PH less than 6.5 for a while to allow your ladies to take up calcium and recover.
I had similar symptoms recently and discovered it was black mould, which was obvious once I got the microscope out when adding calcium did not solve the issue.
As you have an event (too low PH) which matches the symptoms (calcium def) it is unlikely that a secondary cause is to blame.
Too low, not too high. Your ladies would have been fine at 7.2, not optimal but not locking anything out. It was lowering your PH to 5.5 that did it.
