USB ground loop isolation for multiple devices
Can I connect USB hub after isolator and connect 3 devices into a hub
  (that will probably reduce the bandwidth substantially and wouldn't
  really work)?


Yes. I was worried about a similar problem, so I bought a USB 2.0 isolator. The problem is they are pricey (over 200$) because no one makes a USB 2.0 isolator IC. I then plugged the hub into the USB 2.0 isolator and then to the computer. Because the devices were adjacent to each other on a metal chassis, I was more concerned about the ground loop between the hub and the comptuer than the devices. 

It depends on what currents are on the shields of the USB cables. If you have a really nice volt meter that measures uA, sometimes you can dissconect the cables and measure the current or voltage and see if it's worth it to throw an isolator on the cable. 


  Is there any issues connecting multiple isolators to the hub?


Shouldn't be, I've done it and I was fine. Isolators will introduce a slight bit of latency.