My batteries are original. That means they are almost four years old. Here's what I do:
1. Keep the water level topped off on the house batteries. When I got the coach, I installed an easy fill device I bought from Camping World that allows me to fill both batteries by pumping water out of a gallon jug of water into a tube that fills all the cells at the same time. I do this pretty much monthly.
2. Keep the coach plugged into electricity. That keeps the house batteries charged all the time.
3. Installed a Trik-L-Start unit between the house and chassis batteries that keeps the chassis batteries charged all the time.
http://www.lslproducts.com/TLSPage.html
It looks like you are going to have to replace all four batteries. When you do, I highly recommend you follow the procedure outlined above to put off purchasing new batteries in the future as long as possible.
Good luck,
TxTC