Infected with what? Other than being slightly off color, they look fine to me. How do you water and fertilize?

I would also say that box does not appear to be nearly deep enough to grow potatoes successfully.....how deep is it?

Thank you for the response. I read there could be a few different things going on, as far as infection, I'm not sure exactly but leaves turn yellow an die. Watering daily, fertilize once a week. Been very hot in this region. Box is about 7" deep. Was successful 2 years ago in same type of box.

I suspect the soil in that very shallow box is just heating up too much and stressing the roots. That would account for yellowing and drying of the lower foliage for sure.

Potatoes are not necessarily considered deeply rooted plants but most sources will indicate that they need at least a 12-18" soil depth. Plus the mounding of soil one does to increase tuber production along the stems. I would personally never attempt to grow taters in such a shallow bed/box........nor would I consider any other veggies appropriate for that depth other than salad greens or maybe French radishes except for on a very temporary (i.e., seed startling) basis.

YMMV

It looks like they need nitrogen. The frequent watering is washing it out faster than you are replacing it. Are you using a liquid fertilizer. I agree with the comments above - not an appropriate growing box for potatoes.