The kitty litter pail potato plant has now been relocated to a sunny window with an eastern exposure. The fluorescent lamp just wasn't big enough to provide light to all of the leaves any longer. However, even with the new location, it looks like the stems of the plant are getting leggy.
Unfortunately, I am getting worried that there may be more problems with this plant than just poor sun exposure. The leaves are all curling downwards and some are getting necrotic. To me, this seems like a leaf curl virus infection, but I'm not sure. All of the leaf curl virus pictures I have found so far describe the leaves curling upwards, not downwards. I suppose that this might also be some sort of nutrient deficiency. Hmmm ... maybe I gloated too soon about having success with store bought potato seed.
The sweet potato slips are still growing. Soon, I think I'll have to pot the slips from the orange potato. The yellow sweet potato still has a long ways to go.