How do you know when your reeds are too thin?

Question:I recently purchased two boxes of Rue Lepics, size 3.5. I've been playing on them for awhile with a Vandoren M15 mouthpiece, and they've been working well. But recently, I can get a sound out a little too easily on them, and my middle register (third space C to C above the staff) is hard to tongue quickly in, because I get a grunting noise. I know I'm not tonguing wrong, because this never used to happen. Should I try moving up to a Rue Lepic 3.5+? What can I do about the boxes I just bought? One is completely unopened.
I play Bb clarinet, by the way :D
I'm playing on a Buffet B12

Best Answer - Chosen by Asker: I recently purchased two boxes of Rue Lepics, size 3.5. I've been playing on them for awhile with a Vandoren M15 mouthpiece, and they've been working well. But recently, I can get a sound out a little too easily on them, and my middle register (third space C to C above the staff) is hard to tongue quickly in, because I get a grunting noise. I know I'm not tonguing wrong, because this never used to happen. Should I try moving up to a Rue Lepic 3.5+? What can I do about the boxes I just bought? One is completely unopened.
I play Bb clarinet, by the way :D
I'm playing on a Buffet B12

yeah you should, or it might be that your clarinet is damadged, caz once mine was doing the same ting i took it to mi teacher n he moved a few a keys around and he told me that one of tehm was stuck... but anyway... usually if your read is too thin the clarinet will not compromise well with your breathing because the air will escape too easy but dont go up too much or it will get tiring to play

I use a RICO size 2, and I get a perfect sound out of my Bb clarinet.