High water bill. Meter not spinning

[Neal Royal]

I'm baffled by how a property's water bill is so high despite there appearing to be no leak. Multiple plumbers said they don't see, hear, or smell a leak. Meter isn't spinning like it when I got the water main replaced. No silent toilet leak after doing a food dye test. City said the meter isn't broken. 

Can it really be the tenants? All signs point to a tenant consumption issue, not a leak.

• Avg. bill before May: $120
• May: $480 (water main replaced due to leak)
• June: $303 (lowered but still high due to timing of replacement and billing cycle)
• July: $413
• August: $479
• September: $282