I've gathered that DGIV more often manifests itself as ulcers, darkening of body coloration and lethargy so bloating/dropsy may still be down to organ failure or a baterial disease instead. If this is the case, antibiotics could potentialy help though it's highly unlikely if they have already stopped eating. If they are still eating, try giving them some peas as well so as to completely rule out constipation. To be honest, I would suspect the virus - it's apparently quite common in the UK - particularly if you bought them recently. If they have stopped eating and are only getting worse, euthanasing them is the best course of action (use clove oil) and make sure you dispose of them by throwing them in a bin or something as flushing them may introduce this disease into local waterways - which you realy don't want to be doing.
