Could be that you're playing on a Jet-Tone.
This is an ignorant statement. You're perpetuating the notion that they're harmful mouthpieces - maybe because you don't personally like one you've tried (for what it's worth, by the way, they're not all the same, and you're looking at a vastly different rim/cup design with the Maynard models), or someone told you to hate them.
For lead - try a Bach 3F or 10 1/2E, or a Yamaha 14A4a
And then you give OP a cup diameter range that makes no sense. The 3F and 14a4a are basically the same diameter, but the 10-1/2E is significantly smaller. I'm thinking you're not aware of that, and are still regurgitating what you've been told.
When I got to college, my private instructors mocked me until I threw it in the trash can.
I'm sorry to drag your private instructors into this, but this doesn't sound like a environment conducive to learning. Rather, it was their way, or the highway.
When you get a real mouthpiece, your range WILL go down. Keep that in mind. But your consistency WILL go up. Also, as you make the transition, keep the Jet-Tone handy for life-or-death performance situations.
Your statement is ass-backwards in so many ways. Here's why:
You're being ignorant again, in judging other people's equipment based on what you think is universally correct.
If you're playing on a mouthpiece that functions well for your face (which should be the gal here - not impressing somebody with your gear), your range should be accessible, and not be hindered. Why would somebody play on gear that makes their job harder for what they're going to be playing? Who has ever give you that advice?