As we have now learned, changing the feed mix from 1/2 grain and 1/2 alfalfa to 100% grain can be a shock to all the animals, but is a specific shock to the ones who get the most irregular amounts of food (the ones who get pushed around the most), especially if they suddenly consume more.
I force-fed Loki a handful of baking soda two nights in a row. This was the correct thing to do. The next action is to feed both him and Jake a squirt of probios (good digestive yeastybeasties) and get them interested in some hay/grass/anything but grain to get their rumens back to speed.