"RichardS" noaccess@invalid wrote in a message:
snip
Asked one of the staff about this, and their reply was that yellowing
leaves was a classic sign of this deficiency, and if this happens just use
one of the specific XXX fertilizers to restore the balance. It gets
washed out of the soil due to the large amount of water that toms
need. I'm sure that someone can confirm/deny this...
---
I have had the same yellowing leaves problem with my tumbling tomatoes. I
was told that as I used a compost recommended for hanging baskets, I should
be giving my toms double strength of liquid tomato food over the week, thus
doubling the magnesium and giving them extra disease resistance. This I have
done for the past two weeks, and I am happy to report that there are no more
yellowing leaves.

Bella