My memory is usually pretty good, but remind me -- these slugs are from Florida, right?
If so, I think that you have Elysia clarki, as this species has digestive glands running through the sole of the foot, thus the sole is green. The other common Western Atlantic Elysia spp. has an opaque white foot. E. clarki also has a small anterior midline gap in the parapodia, which yours seem to have.
IIRC, this is good news for you and your slugs, as this species has several advantages going for it. First, Elysia spp. are "sap sucking" "solar powered" slugs, which means that they remove the intact working chloroplasts and/or other plastids from algae and these plastids continue to photosynthesize within the slug's branching digestive system. While many Elysia spp. are only able to keep plastids for a few days, research suggests that E. clarki can maintain its plastids for a month or more.
Another "benefit" of this species (and for those who are caring for it) is that, IIRC, these slugs have been maintained in the lab as adults while only being fed a juvenile diet. As it is not fully understood what makes a juvenile slug switch to an adult diet, you may want to provide the algae this species is known to feed on. According to Nicholas Curtis, who has worked with this species, "... adults in the field sequester chloroplasts from two species of Penicillus, (P. lamourouxii, P. capitatus), and two species of Halimeda, (H. incrassata, H. monile), however, juvenile slugs in the laboratory will only feed on fine, filamentous algae like Bryopsis or Derbesia."
Most of this information can be found on the wonderful seaslugforum, which is a great resource. Its so rare to get such good data like this on a sea slug!
Thanks for posting the photographs - they are great. I'm so glad that some of the clarki survived.