I just "googled" Blossom End Rot and it is exactly what I have! The pictures show identical images! I think it's just the one container that is affected at the moment and I suspect it's the one that I flooded out the other month!
One of the tubs fell over in the wind and about 1lb of green toms fell off so I made a green tomato chutney. Should I use the green ones now that are not rotted yet?
