Leaking hot water heater - help

[Justin Case]

I have a leaking hot water heater. It is not leaking much at all and I cant find where it is even coming from.
I starred at it 10mins and did not see a drop but the floor is wet.
I believe it is leaking from the top under the ridge where the metal cover ends since i see water mark stains on the ridge and top half.
My tenants said the city was messing with the street water lines and then they noticed the water heater leaking immeaditly. They think it was the pressure of the street lines.

The water still heats up asap.

I know nothing about the water heaters.. How can i start to trouble shoot this and find the leak around the tank?

Thanks