[3 allotments]

It almost looks like they have been sunburnt after water on the leaves from the plastic gh roof maybe?

[Yorkie]

I agree with your comment about over fertilising. However, we don't know how smellykipper has treated the plants so far. Because these three plants are from different sources (and we don't know whether there are others with different features), he may not have fertilised them at all which could also be a problem.

S/He has already said FBB has been applied.

[devonbarmygardener]

My 'sweet million' grown from seed have gone like this and I think they've had it!
The leaves started going very pale, then white and now they're crispy