Aster Plant leaf problem

I potted on my young aster seedlings in 6 x Plant trays and things were fine.
Then a couple of days ago I noticed odd plants in different trays had developed
"crunched up" leaves on part f the plant!
This morning I noticed a couple had died back!
Any ideas and what action I need to take please?

Thanks . .

 

David, unless you can see insects of any kind under the leaves, I think your plants may be stressed due to moving them. If they are all the same size as the one in your photo, they are getting a bit big for the 'pricking out' process, and may have damaged roots due to moving them at such a late stage..... it is also very hot at the moment
The best thing I think, is to put them in a shady place, water them daily, and wait to see how they recover. Good luck.

 

I tend to think it is probably something they will grow out of, un less of course, as Tetters says, you can see insects on the new growth.
Could be greenfly.

 

Many,many thanks I will take that advice!

 

I'm positive that you are correct! Thank you . . .