Water Heaters - home owner

I just purchased this home that has 3 40 gal vanguard water heaters in a line. The problem is that they have been sitting for about a year. The house is in a cold environment so they had to be winterized to keep from freezing. They have been empty. I went to fill them and found that he relief valves wouldn't close all the way so was very difficult to fill them up. I was able to close them most of the way and they filled. I went to the panel box, turned on the circuit breakers and waited to see if the water would get hot. Well, it didn't. I went back down in the basement and water was coming out of the first tank's relief valve. I have purchased 3 new relief valves but am wondering about the heating elements. I can't hardly believe that all 6 of them are shot, unless the circuit breakers had been turned on when the tanks were empty. I don't know what kind of elements are in there but think I can take the cover off, exposing the wires to the elements and check for voltage across. Is that what I should do or does someone have another idea of what I could try?

It's very possible that it has been disconnected from the breaker(s) to ensure that it couldn't be turned on with no water.

Also, the t-stats could have tripped, check the reset buttons and check that they're at the proper temperature setting.

If you have a multi-meter, you could ohm the elements with the power off. A 4500 watt element should read around 13 ohms.