Perhaps you sowed too early?

Hmmm, not really. I don't use a propagator or anything like that so if it
gets too cold the plants either stop growing or I can bring them indoors.
This is something that I rarely have to do and means that I can be picking
cucumbers by early June and tomatoes by early July. I also do a second
sowing mid-May and harvest those in mid-august when the earlier plants are
starting to be past their best.

But Nick, this April is much more normal as regards temperatures, I agree
a it on the chilly side. You might have to get used to it though! Last
year as exceptional, not this.

I agree that this April hasn't been exceptional, even for down here but the
persistently chilly nights for the last two weeks has been unusual and that
is what has been causing the trouble as the days have been reasonably warm
(especially in the greenhouse) and sunny.

Somebody did say to me yesterday that the leaf damage to the seedlings
hasn't been the cold but scorching from the sun. He may have a point and I
might have to paint some 'cool glass' on the greenhouse.
_______________
Nick G
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk