Potatoes (of at least some varieties) seem to cause blossoming problems for other nightshades (e.g. tomatoes, eggplant, peppers) planted within 10-20 feet of the potatoes.
Ran into that a couple years ago, fortunately, everything was in containers so I could move the potatoes away from everything else - which seemed to make everything healthier and start bearing fruit. One of the advantages of experimenting with plants in containers.
The book Carrots Love Tomatoes is a pretty good source of information on the topic as well (for both beneficial and incompatible parings).