Yellow mange tout leaves

I planted out some mange tout plants (about 6 inches high) a couple of weeks ago, and all the leaves from about half way down have gone yellow - any ideas what's gone wrong and what I should do? Do pea/mangetout plants need feeding ever?

Peas do this if they are stressed. Too dry, too wet, too cold, too hot or just the stress of transplanting.

I've had this problem with my mangetout down the allotment as well.  They are very yellow, almost white, on the lower parts of the plant.  Top growth is still fairly green.  I fed them last night to see if that helps... Will let you know in a week or so if they have greened up!!