potato plants gone black and mushy

Hi all,

Ive been growing potatoes in the ground and in  bags. I didnt get round to building up the soil over the plants in two of the bags until the plants were really tall out of the bags, now the plants have turned black and gone to a slimy mush.  the other bags dont look too bad but some of the leaves have brown spots.  the potatoes in the ground all look okay.

Ive got rid of the 2 mushy bags and there were enough new potatoes to do a couple of meals.  My questions are: with this spread to my other potatoes, can I eat these potatoes from the mushy bags and should I throw the bags away or can they be cleaned and reused.

Many thanks for any help

Jools