Can anyone shed light on this conundrum? I grow these most years as
bedding plants but the last couple of years I have had trouble.

The orange ones are all fine and perform well with big pompom flowers
and so do the lemon ones right up until the point where I plant them in
garden soil. The lemon ones then suffer a growth check and their flowers
seem to suddenly become much more vulnerable to water damage from rain
and parts of them go black. The orange ones all romp away.

The weakened lemon flowered ones quickly become slug fodder!

It happened exactly the same last year too. It cannot be frost damage
and it wasn't drought either. It might perhaps have been water logging.

But I am mystified why all the lemon ones curled up their toes two years
in a row and yet the orange ones are all perfectly happy and growing well!

Any ideas what has happened here?

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Regards,
Martin Brown