Need help on dual water tank hookup

Hello everyone I hope someone can help. I purchased a home recently that used to be a rental property. The owner when converting to a rental had a second pressure tank and water heater installed on the main floor. So here in lies my question. When we moved in hot water worked fine. Hot and cold water workes in the basement where the original tank is also works through the rest of the house however when the fuze blew in the upstairs tank the water went cold through the house.

After looking at the pipes in the basement I discovered that the cold water from the well splits off. One side goes to the pressure tank and the other goes upstairs somewhere, it goes into the wall and i think maybe up to the second pressure tank but I’m not sure. Now this is what is confusing me. The input for the cold water line in the tank downstairs was turned off. No cold water was coming in to the tank but the tank was turned on and had hot water in the hot water pipes. So just to see what happened I turned the cold water intake on for the basement tank and boom hot water through the whole house again. I have had the power and cold intake/hot output valves turned off to the main floor tank for a week now. Basically bypassing that tank all together and the only thing I have noticed is we run out of hot water faster.

So the question. Should I leave the cold water input for the basement tank on as well as all the valves and power on the main floor one or should I turn the cold intake back off downstairs.

It sounds like your water heaters were plumbed in parallel, the upstairs was the one heating all the water and the one downstairs was prevented from pushing hot water through the house because the cold water valve was off. I bet the one downstairs is a smaller heater or possibly not working to it’s full capacity. Originally the thought would be to have more hot water to all the fixtures throughout the home faster. Not sure why someone would have turned off the cold water on the tank downstairs. As long as you don’t have any leaks I see no harm in leaving everything on. Sometimes when a home is empty for awhile the water valves to water heaters are turned off to stop leaks if the water heater was to fail and perhaps this valve was just forgotten to get turned back on.