Has the temperature gone up in the tank since they've been gone? There is just as good a chance this is an infection rather than gas bubble disease. If the tail appears to be floating and the bubbles appear to be clear or air filled, then it is probably GBD. If they are opague and do not cause the tail to float up, then they are probably a manifestation of a bacterial infection. Either way, I recommend the following:
Be very meticulous about rinsing the mysis before you feed it out, and cleaning out any leftovers using a turkey baster. It will help keep the water pristine and reduce the chance of rising nitrates or ammonia.
Try to bring the temperature down in the tank to the best of your ability to somewhere in the 68-74 degree range. If the bubbles are an infection, rather than air filled gas bubble disease, then this will at least slow the progression of the infection until the owners can get home and the decrease in temperature may even take care of it on its own.
Add an extra airline or two also. This will decrease stress, and may also help aid in GBD if it is being caused by an increase in CO2.
Edit: I just noticed they are in your refugium. I still suggest trying to bring the temp down, although I realize this may not be possible in the refugium, and you may need to move them to a different tank to do this. Do you have any syngnathids in the display tank (seahorses, pipefish)?