Hey, so this is my first post, so let me give some background, then my issue. I've been playing for about 10 years now, have a Strad, and use one of those interchangable Warburton's for my mouthpiece. I have a range up to C, sometimes up to Eb (above the staff). Anyway, I've been encorperating Caruso exercises into my routine when I play. I make a conscious effort to not use too much mouthpiece pressure, to stay relaxed, and take very deep breaths. However, instead of getting that numb, flabby feeling in my lips, they just straight up stop vibrating. I won't even be exhausted (I think) and they'll just stop. I've tried increasing air flow, making sure my mouth is open, and all that, but it doesn't really change that. Keep in mind this happens to notes I can actually hit (usually D) and has no effect on my overall stamina. Do you guys have any ideas? I feel like it's been stopping me for a bit.