Do you think its both of them or just the one? Hard to tell I guess :?
How big are the bowls ?
Average water consumption is 50-100ml/kg/24hrs
Just checked the jug I use to fill water. I'd say between 700-800ml each time I fill the bowl. They don't eat much hay, some days they do, some they don't. Not like my others. Its hard to say who's drinking it all aswell. I feed them separate as Phoebe eats more than Albie and he doesn't get his fair share. Nothing has changed food wis e. Hay varies each time I go I suppose. Always feed similiar veg and herbs.
Have they had a Dental check recently ? Dental Rabbits can drink a lot to try to fill themselves up (eating may be painful) and also to soothe a sore mouth. The fact that they are not good hay eaters may point towards Dental problems
Do you weigh them regularly ?
What is their wee output like? My bridge bun Mopsy had diabetes insipidus. She would drink 3 litres a day and I had to change her litter tray twice a day or she would flood it. If I were you I would try to sit and watch them to see who it is that's drinking lots and then maybe get a vet to check them over. Hopefully its just because the weather is warm but best to be sure.