Fortunately, this does not look like Late Blight. (We're assuming this is the "blight" you were referring to, since several plant diseases have "blight" in the name.) The blackened stem might be simply abiotic stress (due to environmental conditions and not a pest or disease). If it were a disease, then Southern Blight is a possibility, but the symptoms pictured don't strongly suggest that diagnosis. To make sure, and to discourage Southern Blight going forward, you can move the mulch away from the stem a few inches so it gets better air circulation. The characteristic mycelium (fungal threads) and spore capsules described and pictured in the page linked above can be diagnostic if found, but if not present, that infection is probably not occurring.

Leaf edge darkening might be due to drought stress or under-watering (even if only temporary, since leaf damage cannot reverse itself), natural leaf senescence (preparation for shedding), or perhaps leafhopper feeding. If you brush a hand through the foliage, see if any pale green wedge-shaped insects jump or fly off, which would suggest leafhoppers are around. At this point in potato season, no management of leafhoppers should be needed if the symptoms are not severe (they do not appear to be).

Miri

Thank you!

Thank you!

You're welcome!