It seems as if L.rubellus is difficult to find and often confused with both E.fetida/andreii when small and E.hortensis when adult. I'd wager you have E.hortensis, especially if they have a slight to moderate excretion of the yellow-geenish liquid.
Personally I would guess that most E.hortensis cultures have both E.hortensis and L.rubellus which would explain that sometimes you get worms that excrete and sometimes worms that don't.
I have to say that E.hortensis is a good feeder that doesn't get refused a lot, however I can see a clear distinction between the acceptance of L.terrestris and E.hortensis.
I have seen several different reports of the growth rate of these worms at different temperatures. The optimal temperatures also seem to differ very much depending on which scentist wrote the article...
Dendrobaena veneta = Eisenia hortensis:
E.hortensis growth rate article
E.fetida growth rate article
L.rubellus growth rate article
Conclusions from these articles:
E.hortensis max. reproduction rate seems to be about 2 cocoons per worm per
week@25C which seems to be a more optimal temp than 15C for this species.
E.foetida have very low reproduction rates at 15 C. Their max. reproduction rate seems to be 10 cocoons per
week@25C per worm.
L.rubellus had a reproduction rate of about 2 cocoons per
week@15C per worm and quite suboptimal conditions.
I guess I'll have to find my microscope and get to work separating L.rubellus from E.fetida/andreii(these two can only be separated on a genetic level...) and E.hortensis.........lol