I don't think an aquador will work on this type of skimmer.
If I'm looking at the plumbing right you have a 3-way valve that will isolate the skimmers from each other. That's a good thing.
I'd run the bucket test with everything open, with the pump running and with it stopped.
If it leaks more with it running than with it stopped your leak is most likely on the discharge side of the pump.
If it leaks more stopped then it's likely on the suction side.
Then if it leaks the same amount or less when running, I'd close one skimmer and plug the port in the bottom of it and run the bucket test again.
If the leak doesn't change, switch skimmers and run it again.
If I'm looking at the plumbing right you have a 3-way valve that will isolate the skimmers from each other. That's a good thing.
I'd run the bucket test with everything open, with the pump running and with it stopped.
If it leaks more with it running than with it stopped your leak is most likely on the discharge side of the pump.
If it leaks more stopped then it's likely on the suction side.
Then if it leaks the same amount or less when running, I'd close one skimmer and plug the port in the bottom of it and run the bucket test again.
If the leak doesn't change, switch skimmers and run it again.