Gill,
It is a delicate balancing act to provide the plants enough water for proper fruit development - - but not too much as it causes the tomatoes to have a watered-down taste to them. Putting in 100% Potting Mix in a SWC like the EarthTainer or other Commercially available SWCs saturates the plants with too much moisture.
You can see in the above photo how this excess moisture causes the bottom leaves to prematurely yellow and die. Here is another photo where the Moisture Meter was pegged on "Wet":
Conversely, here is a Cherokee Purple from this past Fall's crop in the 3:2:1 Combo Mix:
I think you can see the difference. The Moisture Meter read in the "Moist" range.
My point was that when you see wilting at the tops after a few days of hot weather, you may need to manually add a pint or quart of water to the plant. This should not be the "normal" (wilted) day-to-day condition.
Raybo
