Posted: 15/06/2014 at 14:55
Cress is a brassica, and you wouldn't let that grow so big before you cropped it. Most salad leaf mixtures are brassicas.
Sow the other packet, but harvest the seeds as soon as they are big enough to put in a salad.
I still think the fault lies with you not the seed company. I think everybody is too kind to tell you; or they are not gardeners.