How long have they been having potatoes? as if you introduce something new into their diet it can take up to a week for their poos to settle down. If they have only had one day of runs, I wouldn't really think about giving them antibiotics as you say you've introduced something new. If you use antibiotics too quickly then you can get resistance in the future.
Are these 5 litters your first litters? or have you not change something in their diet in the past? Do the ones with runs live in more mucky conditions? as this can cause runs too (antibiotics may well be needed). Or do these litters with runs have more piglets in and worse off looking mums?
Anyway the antibiotics are up to you, but its probably down to the pots rather than an infection/virus as the others would have it too, unless they are kept elsewhere.