hey Tem I dont grow in hydro so cant help there but their is a few Questions I can ask . what is the ph of the water you use , do you use air stones ,what is your nute schedule ,how far away are your lights, can you post pictures ,how big are your plants if they are small early plants then they shouldn't drink to much but if they are large then you may have a problem. my plants in bloom are about 3 feet from the ground and they drink about a gallon every 3 days but my plants in veg only drink a quart every 3 days . I do know that all the questions that I asked could all be the problem sorry I couldn't be more help