sweet potato blight?

I've grown slips for this variety of sweet potato from saved potatoes on our kitchen table for more that ten years now https://permies.com/t/17569/plants/sweet-potato-propagation-harvest ...and this year I think I am going to lose them.
This year, I had many healthy looking slips and some I had already cut and put in water to root when they started looking blighted and some died completely...both in the rooting water and those still on the potato. I've composted the worst (our compost piles are not spread on the garden...they are just piles in place where I eventually start fruit tree guilds).

The only thing I can think of that might have done this indoors (carried and spread a virus) would be aphids and I never saw any this year. We had a huge group of 'house' lady bugs though and I found some of them on the plants...I wonder if they could spread anything or maybe they were after aphids that I never saw........I have a few potatoes left that I think I will try to sprout after I give up completely on these. I just would like to keep this strain of potato going even if I can't plant them this year.

I don't think it is the potatoes themselves, as the crop has always had healthy green vines.
I suppose they may have 'played out' and become less resistant to a virus. The original sw. potatoes were given to us by someone who had grown them for years and years...

any ideas?

That looks like spider mite damage to me. Look very carefully, with a magnifying glass if you have one handy, for tiny round red mites. If there are a lot of them, there will often be a bit of webbing over the plants. It's a big problem with plants indoors in the winter in low humidity conditions. If you catch them early you can control them by repeated sprayings with water, or turning the pots upside down and swishing the tops in some soapy water. I rarely see this outdoors at all, so if you can get the plants to survive till it's time to set them out, the problem should go away.