I noticed today that the lower leaves of most of my Pink Fir Apples
potatoes are turning yellowish, and some with black spots.

Is it to early for blight? Last year all our tomatoes succumbed to
blight but I seem to remember that it was later in the summer. I'll be
very unhappy if it is blight, as I have about 160 potato plants in,
and I can't bear the thought of losing them all.

It's my first year of growing potatoes so I'm not sure what's
happening. Any advice would be very welcome.

Will