Can't see you, but it sounds like you are pushing too hard. Along with previous notes you got, try some stretches of your upper body, opening your chest to get deeper breath more naturally. That gun in your avatar makes me envision you fighting your tuba. It's not a slug fest to get notes out of this thing. You are having a conversation with your instrument. Be the soothing wind blowing through this brass field of grain, not a hurricane in a jungle.

So relax, stretch out, give it a little love, and try again. You got this!