Sickly looking sweet peas

Hello - I haven't been on here for a while!

I planted some small sweet pea plants in my newly filled raised bed about a fortnight ago.  Not knowing a lot about the soil (it was a delivery from a local reputable place) I dug in some compost to the top layer and threw on a good load of chicken poo pellets which had dissolved in by the time I planted anything.  But I've been noticing that some of the leaves look a funny colour, ie not a healthy green, and although they are still putting on growth they don't look as though they're really thriving.  Does this mean they are lacking some minerals and need some extra fertilizer, I know they're heavy feeders, but what should I put on them or not?  We have had some cold spells, and the odd snow and hail but I wasn't sure if that was the real cause.

What do the sweet pea growers out there think?

It could be the first set of leaves dying off, or any number of things, is it just the bottom set of leaves ? or is it working it's way up the plant? They do like a good feed, but it sounds as tho' you have it covered. Try some epsom salts watered on to them it may help if it's a magnesium related deficiency.