When you put your mask on... Which straps are you tightening first? I was told by the people at OTS to begin at the lowest strap and work up. Adjusting your mask this way will give you a better seal most likely, and you shouldn't have water leaking issues.
With the AGA FFM yes start with the bottom and work your way up and when you reach the strap on the top of your head it should just be snug not tight or else it will pull the mask upward. I dont even tighten the top strap any more then a quick pull and it is fine. I am sure AGA OTS and the rest its all the same.