Yeah, just as Chewie said and you have already stated, you lack depth meaning you have to pretty much play the same XI every game and it doesn't look like you play 2 of your seniors (both rested) so maybe try and slot them in along with youths into your senior team.
But when you look at both my teams, my lowest is satisfactory (my best bat and my captain and my best bat scored 160 odd yesterday which won't help his fitness), another couple passable (my oldest player and my youth which I'm getting experience by playing in most games), another 3 energetic (my T20 skipper, and a couple of batsman, one who made 159 yesterday) and the rest are revived or rested, not to mention it's the end of the week so everyone should be back at revived or so by Tuesday and if not, I can rest them.
It does help that I'm not trying to do anything in seniors as I'm focusing on youth but it can still be managed. Try and get a few more fill in players in your senior squad, which you can pick up for not much and have them play a few games, while not costing you too much in wages.