When was the last time they got a dose of calcium? (1 tsp molasses per gallon of properly ph'd water per week)

Ingoing water ph is a tad high as already mentioned, but not drastic. Would be nice to see an accurate runoff ph. The buffers in the soil don't last forever. Might be that it's losing it's ability to buffer properly. (soil ph drops as the buffers fade..especially with peat-based mediums)

Do nothing drastic nor heavy-handed. They're too deep into flowering to be messing with 'em too much. Nothing but straight, properly ph'd water for a week before harvest.