If you are taking supplements to help with your power-lifting, you might want to research their side effects. Specially if you are "supplementing." It might also be related to post-workout recovery if you are hitting the range within a couple of hours after a workout. The hyper-hydration is also high in the list of suspects as you are flushing a lot of electrolytes out of your system. You really should cut your water consumption at least in half. Remember, a lot of the training advise you get from your buddies, read in a magazine, or hear at the gym is BS, gym lore, and mostly down right wrong. Just like advise you get on the internet.