I'm still having issues on my iPad Air with iOS 9 (I don't remember what exact iOS version I have).
I was just looking through the bug that we filed with Apple. drzissou had been kind enough to send us the Bluetooth diagnostic log from his iPad and an accompanying video, and in the video he showed that in the Blutooth Settings screen if he clicked on the buttons to connect to his 2 H9s quickly then both would connect fine. If he clicked on one, waited for it to connect, and then clicked on the other, then he was unable to connect to both at once. You'll see this in about the last minute of his video:
I just got off the phone with another customer who was having this same problem, and the same thing was true in his case as well. If he clicked on the buttons for both H9s quickly, then he could connect to both. Please try this as well and let us know if it helps.
EDIT: I just realized that I was responding to a post by drzissou, asking him to try a solution recommended by drzissou. Sorry drzissou! Got a bit confused. I meant to address your suggestion to the other people on this thread and not you in particular.