Potatoes grown in tyres

Dear sir/madam,

I have five potatoes plants growing in a stack of four tyres. One of the plants has gone yellow and is dying. I read that this means the potatoes are ready. however the other four plants are still green and one still has flowers. Can I leave the potatoes in there until all the plants yellow or will the ones ready now rot and affect the others?

please advise.

regards,
Alex