Puckering leaves

Hi all
I sowed a lot of seed in 2 different manufacturers composts earlier in the year (I took what was available)
With a 98% success rate I thought both were really good composts. The plants all started growing really well until the last month
Now, 2 or 3 months on from sowing, some of them are not looking good at all. I have a suspicion that it might be that dreaded weedkiller beginning with a "P" that was in the compost
All the new growth looks distorted
I have attached pics of lettuce, chilli and coriander

Hi. Thanks for your reply

Yes. I have checked for any pests, it was the first thing I checked for. I then checked online for another reason as to why its happened, (greenhouse to hot etc ). It has the looks of Aminopyralid (thank you for correct name) and wanted confirmation from someone with more experience of having suffered from it.
From what Ive read, one of the symptoms if you like, is that it doesn't show up straight away in the plants, it only rears its head when there are few leaves on the plant. Im not 100% on that though.

That third photo shows a large colony of green aphids which will cause the puckering. They are probably underneath the leaves on the others.

Third pic definitely looks like greenfly; they have been terrible this year. Greenfly often replicate on the underside of leaves causing the leaf to curl under protecting them from predators. If the plants are small then just squish them bearing in mind that the adults are canny critters and will jump out of harms way if they can 

If it is a larger problem I spray them with soapy water (3 teaspoonfuls in a litre). This kills them instantly but only if you get them wet.

With either technique watch out for ladybirds and their offspring.