Hi! Overall the piece is lovely
I just have a few notes about the trombone part, as a low brass player. Not the trombone 1 part, it's mostly fine and trombones can read treble clef. But the trombone 2 part is another matter entirely.
So, The trombone as an instrument can technically play most of the notes you have listed on the page, but generally you just have them playing really low. If you intend the part to be a bass trombone, it's all fine and well, but it's important to note that normal tenor trombones, even with a trigger, can barely play that Low C, and cannot play the low B natural.
But if you want them to be playing that low, possibly on a bass trombone, you then have them in tenor clef at 193 (Which by the way is not necessary, it's more annoying to have to switch to tenor quickly than to just stay in bass clef and read a few ledger lines, especially considering you go up to a high G. And also the trombone 1 part goes higher but is still in bass clef?????). While professional bass trombonists can hit that high, it's much more annoying than it would be on a tenor trombone.
Looking at general scoring, it seems like you might want to have 2 trombone parts(or just label the staff trb 1, 2) and a bass trombone part, though I understand that with a lot of music notation software it then becomes a space concern of fitting it all on the page.
...I just now saw that this was due on the 10th. I wish you well with the competition! Keep these things in mind moving forward and I can see a lot of growth!
P.S.
The tuba part is great. All good on that front. Sincerely, A tubist