Q.blossom end rot
How often do I give the tomatoes a bath of limestone water? I’ve got almost 200 tomato plants…and they’ve all got blossom end rot. We’re in a drought area, hard hit, and our well is being over worked.

Certified GKH Gardening Expert
If your tomatoes have all ready developed Blossom End Rot, combine 4 level Tablespoons with 1 gallon of water and apply as a foliar spray. Apply to the leaves two to three times per week. The ideal application rate is 1 gallon of solution for every 20 to 50 square feet of garden. Foliar spray of Calcium Nitrate is not the perfect cure for Blossom End Rot. Use a regular watering schedule and fertilizer application for healthy plants.
Here is more information:
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossom-rot.htm