Perfect intro to this month's thread as always Waffle.
Coco, such a tricky one, your question, and could be either a mixture of 30 mins not being enough, or, that your DD has hit that standard wall that comes part way when things are not quite coming together or pieces fatigue is already kicking in, and they haven't even completed learning them all.
My DD also does 3 instruments, though I'd say it's really 2 as one is voice. Interestingly, she has commented this time around (is also studying G8 piano right now) that the pieces are not inspiring her, all REALLY long (vs a shorter one for C) but didn't have the energy to research the non-std pieces before selecting. We only have 30 mins lesson also during term time, but the entry is only put in when she's part ready on at least 2. I challenged the duration once circa G5 time ago, but he said it was enough, given what she does on other stuff.
I recently asked for a 45 to 60 mins lesson from her school violin teacher when G8 entry was proposed (even discontinuing singing, as I didn't think 35 mins lesson time was enough, especially when at school reality is it's less with change overs) but it was declined.
I guess what I am trying to say is that in an ideal world, increasing lesson time would most certainly help. But, these teachers, having known my DD for a while, have taken into account her wider interests and time restraints and worked with them, with no pressure, and it seems to work. Yes the practise time could be longer from her, but they know she does what she can, when she can, and at this age, are working with her more holistically than the parochial way of younger years. It has also kept her engaged in school music life more than some of her peers who are dropping their instruments and ensembles.
I can understand her thinking she's not making progress. I think it's more like G8 is such a jump from the other grades, and it's easy to compare yourself against the DC who have access to longer lessons, go to JD, have more music hours, that you think are never going to make it. Your DD is clearly practicing which is great, just may need to enter later given the amount extra to cover. And if her schedule allows for longer lessons (that make her feel more progress is being made), then great, I'd do it.