Randy,,,,, simply sounds like the air hawk is just more powerful,,,, which doesn't surprise me. My blackhawk is one of the hardest hitting .177's I have and as you know it's the same power plant as the air hawk. If your whisper was losing a substantial amount of power it would quickly reveal itself in it's overall accuracy, especially at longer ranges.
Do yourself a favor though,,,, get yourself a chrony as time and money permit. You'll never be sorry. As the others have said the chrony takes all the guess work out of diagnosing if your air gun is losing power or there's a problem.....
Jeff