What kind of pipes are in the park? Do you have a map showing the location of pipes in the park? Many times pipes get replaced over the years but if park is 50yrs old it probably had galvanized pipe when built.
Water usage is obviously way to high should be more like 100 to 150 gallons a day per home. This would equal about 170,000 per month.
Is there a leak in the mainline or a tenant running water 24/7? One garden hose running 24/7 is 423,000 gallons per month. My point is it doesn’t take a big leak to burn alot of water. With no submeters it is really hard to know for sure but one disgruntled tenant could run a faucet nonstop and use a lot of water. Leaky toilet could use between 500 and 1500 gallons a day.
It sounds like a water leak…
Best way to know for sure is to have some watch the meter at 2am and see what kind of usage is going on.