Yep. Thanks juliuskitty

-- or anyone else -- please do post answers to any questions posted if you know the answer.
Watering IS the issue. I usually do the "stick finger in the soil" test. But actual amount and frequency to water will depend on the size of the container, how moisture retentive the growing medium is, and the number and size of drain holes in the bucket -- how well the water drains out.
In a tall container like 5 gal buckets, the bottom can remain wet/moist while the top has dried out. There would be a gradual level of dryness from top to bottom. I would let the surface dry (putting finger on the surface of the mix feels dry) and water when a finger pushed into the mix about 1 inch still feels little or no moisture (for me that's first two joints of the forefinger) --- but I wouldn't want to let the 2nd inch layer to become dry (first two joints of *my* middle finger).
I have started drilling holes in the SIDES of containers. My two gal buckets get a series of holes at the bottom rim and halfway up. I would drill holes at bottom then 1/3 and 2/3 of the way up the sides of 5 gal buckets.
Temperature and humidity will affect how quickly the mix dries out. Also, when it's colder OUTSIDE, the heater runs more often to maintain the thermostat temp, so the air dries out more.
INDIVIDUALLY, the plants will need water more or less depending on their developmental stage. Once they start setting fruits, they drink a lot more than when they are just foliage. So you need to check them individually and water accordingly. Unlike outside on the ground where the moisture levels will even out somewhat, each container is it's own little world.
I have heard, though not confirmed, that although the term is "foliar" (leaf) feeding, the developing fruits can absorb calcium through their skin while they are still small/tiny. But by the time you actually notice BER on larger green fruits, it's too late.
You do need some calcium in the growing medium to begin with and commercial potting mix --especially peat and perlite type potting mix-- are not likely to have any (or very little). I like organic potting mix that contain compost and mycos (mycorrhizae) when I'm buying them, and use my own home made compost, vermicompost and under the woodpile or leaf pile topsoil when mixing my own. Other stuff I add also provide macro and micro nutrients and minerals -- rock phosphate, greensand, dolomitic lime, Kelp meal, pelleted alfalfa, and sand. I do sometimes add eggshells at time of planting in the bottom of the container, but rarely later on.
Whenever possible, I also add earthworms to the plant pots. On Christmas, I came home with two 1/2 pt containers of "baby crawlers" after visiting with BIL who went fishing and got me extra from the baits shop. ("Whatcha getting your SIL for Christmas?" ... "A couple of boxes of worms."

) He's promised to get me redworms (red wigglers) for my vermicomposter next time -- which may be today since he and DH went fishing for lake trout early this morning
