It sounds like yours are close to being ready to dig. Harvest enough to eat a meal or two from them now. These "new" potatoes are yummy but will not keep for long. Let the vines die back before harvesting any that you don't want to eat right away. Perhaps you can harvest the ugliest plants or most visible plants for early eating and let the others die and dry for good keeping. Days to maturity are guidelines only, the plants don't read them or necessarily obey them. Rain, soil temperature, etc., etc. may all play a part in how long the plants will grow. I hear you on the poor looking plants. The first year my husband was involved in helping with our potato patch, he kept close watch on the plants. He could not understand why they would go from great looking plants to dying plants in a couple weeks time when we had not had frost, insects, or drought. My reminders that they were supposed to do that only made him ask why and how....which I couldn't answer with anything other than "that is how potatoes grow". The harvest was great that year. He puts up with the ugly drying vines for a few weeks now without complaint and helps me find new and unusual varieties to try.

From the pictures there sure isn't anything major wrong with them. Likely some early blight but I sure wouldn't pull them! Assuming they were planted at the proper time it will soon be harvest/digging time anyway. That means all the tops, not just a few leaves, will all start dying back soon. If it worries you you can always use a mild fungicide on them. The light green color could simply be insufficient fertilizer feeding. Dave

No, it wasn't blight. Likely you could have used them.

I just dug up one plant that I stuck in a pot last spring because I didn't have room for it anywhere else. It's my first year growing them, and I just couldn't wait and wanted to see if it worked! I have a nice pile of small but nicely formed tubers from this small pot, so I am excited like a kid on Christmas morning to harvest the main crop later this month and serve my own sweet potatoes at Thanksgiving. Does anyone have tips for curing them on a small scale? I've been reading about giving them heat and humidity to form sugars. If I put them in my detached garage that gets very warm in the daytime (the sun beats in the windows and onto the roof) under a sheet with a pan of water nearby will it work even if the temps go down into the 50s at night? Thanks!