I don't know what the sprouts are except to say they are not any of the seeds you mentioned. Cats are a menace to seedbeds and you need to keep them off newly cultivated areas. You can use twiggy prunings or chicken wire. Don't wait for damage - protect the earth as soon as you have sown.

hard to say, I dont see any tell tell black lesions on the stems. I think it just may be some late season decline. Leave em and see if you cant get a few more nice maters before frost.

I'm pretty darn sure about it being a calamint at least. Square stem, tubular purple flowers. It showed up in my yard and has seeded around a good amount. It fits most photos of Nepitella (although some photos show a shinier leaf). The flowers are lavender and tubular, exactly like most online photos for Nepitella. I have looked for my own photos of it blooming with no luck so far. Does anyone know of other possibilities for it? There's no harm in tasting it since it's in the mint family, right?

Agree. I planted several different varieties of potatoes thanks to a sampler pack from Moose's Tubers. One variety is starting to look awful. It has already bloomed. I have Colorado potato beetles which I try to keep hand picked so I do have some beetle damage but I see none on your plants. This looks like normal aging of plants and they will look worse and worse. I think this is a surprise to new gardeners and it can be confusing since different varieties have different schedules. According to the Farmers Almanac, potato vines usually die by the end of August. Here in NH zone 5-ish, I've dug some new potatoes from a couple of plants that grew from potatoes I missed during harvest last year.