The wee bit of Epsom Salt (Magnesium Sulfate) added to water and dumped on or near the plant really does very little to help with this Calcium deficiency, even though it may be caused by too little Magnesium in the soil (or because there is too much Magnesium) since plants need some Magnesium to properly utilize the Calcium. The best way to prevent Blosson End Rot is to start the growing season with a good, healthy soil well endowed with organic matter so the soil has balanced nutrients and will be evenly moist, but well drained. Mulching the soil will also aid in soil moisture retention, so you may not need to water daily which can create more problems because a too wet soil will also keep the plants from uptaking needed nutrients.

Yeah, it's BER. Paste tomatoes are the most sensitive. And the first few tomatoes a plant produces will get BER the worst. Pick those damaged fruit and discard them if you haven't already. That is a good point about a high reservoir temp possibly causing the problem.

hambone40...epsom salt, a handful under each plant when setting out may help....

You say tomato TIPS, so are you talking about an area of black at the blossom end of the fruits? If so, then the problem is BER ( blossom end rot) which can be a real problem with container grown tomato plants, as well as with those grown inground. If it's BER please go to the top of this first page, click on the FAQ link and scroll down until you come to the article about BER. You can also go to Google IMAGES and type in something like tomato BER or spell it out and take a look at some pictures to see what I'm talkiong about. Carolyn