Supermarket cress

I was in a supermarket a couple of weeks ago and they were selling tubs of cress for 5p. They had loads of them going cheap because they were on their best before date. It was the kind of cress that's grown in the tubs in some kind of paper foam impregnated with feed and water.

Anyway, I ate most of them but there are two left that are now a couple of weeks after their best before date. I've kept them on a window cill, watered them and even put a splash of vegetable feed in the bottom of the tubs to keep them alive.

The cress is much taller now and the leaves are noticeably larger. So is cress still good to eat at this stage? Is the best before date only relevant to whatever feed they put into the tub in the first place?