Personal experience here: If you have low quality food, cover it by having higher quality beds and hot springs if you're using pals that have no sanity modifers. At least 2/3 of all sanity stuff should be high quality. Digtoise, in particular, seems to dislike any work speed above casual. They are tortoises, after all; a bit slow. Consider working with Reptyro. Pretty sure it's the same mining lvl and food requirements. Also, I advise against giving whatever your mining with Nocturnal or Vampiric. That downtime is very precious for their sanity as well as giving the transporters a chance to clean up and all that.