After 142 days of growing they should be fully mature, esp seeing the new roots growing from the skins, not sure why so skinny unless due to a soil nutrient or watering deficiency.

Agree they are as big as they are going to get. Looser, sandier soil, more water and more nutrients next time.

Dave

I gave my sweet potatoes very, very little water [to help against scurf] what with a good plastic mulch cover and tight holes for the vine stems. Still, they got huge. I would look to planting technique and fertility.

Those appear to be a purple sweet potato. Are they purple inside and out. They look perfectly normal to me. The purple ones are usually longer and not as big around. I just finished harvesting over 800 pounds of them. Sometimes you get bigger ones, but they really do vary in size. They are a very long day to maturity

If you can leave them in the ground, I would. They will put on more size.