I have to agree with TubaLawLisa and voiceofreason. On the surface, it would appear that at least part of the issue may be resolved by planning your playing day better. I've known a lot of tubists, especially younger ones, who don't always
plan their playing day, i.e., taking steps to assure they are preparing for the needs of the day, the week, the month. They simply head to the practice room (or rehearsal room) and blow. Then, when the audition comes, they say, "But I practiced, like, 4 hours a day." To which I've said once or twice, "Maybe not. You may have played for four hours a day, but if you didn't produce the desired results, your time spent was entirely ineffective." As an undergrad, I had a couple classes that started at 7:30 am. I've never been a morning person.

But it only took one time for the professor to look me sternly in the eye and say (in front of the class), "There's a problem...
fix it." I would echo the same words to you.
For all appearances, the fix lies in your hands. I set the alarm for 6 am so I had enough time to roll out, wake up, and get my a** to class. I invite you to consider the same possibility for yourself in planning for your daily playing demands. Your warm-up does not have to be immediately prior to rehearsal. I'd bet that if you got in 20 minutes of concentrated warm-up before your 8 am class, you'd notice a difference. Or 15 minutes...or 10.
I did a master's in performance. Then I did another in orchetsral conducting. I felt EXTREMELY well prepared to "enter the real world," toward whatever opportunity arose. I took a lot of that for granted. Six weeks after finishing the conducting degree, I was preparing a tape to send in for an audition. I asked a fellow grad student to offer his opinions on my playing. I played. He said, "Uh...I'm not sending in a tape." I felt extremely well prepared. That night, at a friend's house, I ate something that contained something to which I was extremely allergic. Things got so bad that the doctors pretty much gave me a 90/10 chance; 90% chance I would expire before the night was out, 10% chance that if I survived, it would be in a persistent vegetative state. One doctor's opinion was that if I were to wake up and be able to recognize my name, it would be a miracle. So what if I had to relearn how to speak, to walk, to hold a fork...retaining the cognitive ability to respond to my name would be a miracle compared the the outcome they expected. But...when I woke up I was pretty much all there. Except...my vital lung capacity went from 5.2 liters to 1.7 literally overnight to to a lung that ruptured under pressure. Somewhere in the midst of that, it displaced a rib (pushed it out of its cartilage socket near the spine). After a couple months, the persistent discomfort and radical change in what I was capable of producing was completely disheartening and showed no sign of turning around. I sold my horns. So it would just be conducting.
Except...I'd had a pretty photographic memory. The extreme lack of oxygen to my brain resulted in really swiss-cheesing memory. As a side note, I remembered nothing from high school; I knew when and where I went to h.s., but could not recall a single person or event from that period of time. Everything prior to the event was like that. I lost entire chunks of my childhood. Anyway, I had conducted from memory a lot. I knew Brahms 2 cold. But I was conducting a performance and got to a section just before the second ending in the first movement and lost it. It was gone. I ahd no idea where I was in the music. I don't know why it happened, but it did. I would find scores in my file cabinet and not remember that I'd ever worked on them. I once even found a score that I was certain was someone else's, because "I had never had that," but when I opened it to look for a name, there was mine. And the score was fully marked, analyzed, etc. In my handwriting. Needless to say, it was a knock to the confidence level.
Eight years later, I still experience daily side effects of that one night.
But it's time to be authentic with yourself. My situation, as much as I could say that those friends were aware of my allergy and had assured me what food was okay (and had clearly been wrong), ultimately, I am the only person who puts food in my mouth.
Once you are an adult (or for that matter, as early as you are capable of stringing together conscious thoughts), you are the only person responsible for the outcomes you experience. You are the person getting up when you do. You are the person in charge of determining your playing situation. You are the person choosing to attend rehearsal. You are the person choosing to respond to the conductor's (IMHO) unreasonable demands. You are the person choosing to travel the same daily route expecting to wind up with a different outcome.
Posting here is devoid of tone, so I invite you to consider my opinions not as chastising, but rather entirely encouraging. Your post reads as though you're the victim (loosely using that term), where these things are
happening to you as though you have no part or no choice. I encourage you to work toward a paradigm shift that allows you to instead view your situation entirely in terms of what you are creating for yourself. While "there's only the here and now," if you want, or expect, a different outcome tomorrow, you must change your actions now. Reprogram yourself to think in terms of -ing, instead of -ed. It's a simple, semantic thing, but you may find a big difference in the results you're achieving.
So, yeah, short story long, you're griping a little bit. Those people in Iraq? They've got problems. You've got something you can easily impact, if not fix entirely. You're still playing, you're young. Use it wisely.
Best of luck,
Mitch