I am having the same problem with my iPad Air.
I can connect the first H9, but when I try to connect the second H9, the bluetooth light on the second H9 lights up for a brief moment then goes out. On the iPad, it says "Connected", but after a few seconds it changes back to "Not Connected".
I recently purchased an iPad Air 2. It is able to consistently connect to both H9's simultaneously.
It must be something with the iPad Air that is causing the problem.
My iPad Air is running iOS 8.1.2, while my Air 2 is running 8.1.