The main issue is likely that you are cleaning too much - you can’t really do that with boys, particularly as yours are young/coming up to teen boys.
Obviously you need to make sure the cage is dry and that you poop pick the cage each day but otherwise doing too much too often (of bedding changing) can make things worse.
The more you clean, the more they will scent mark again, the more it will smell.
Changing bedding too often is a new territory change for them which can cause a new round of dominance.
Changing out half the bedding at a time and wiping the clean bedding with soiled bedding to transfer some scent can help them not feel the need to scent mark so much.
But, teen boys are a bit of a testosterone filled delight and it can get a bit…..fragrant!
Make sure the air the room each day.
What absorbent layer do you use under the fleece?
Piggies cannot be litter trained - they are going to pee and poop everywhere - but yes you do need to remove wet hay each day.
What do you require money saving ideas with? If you mean hay wastage, then there is no thing as wasted hay! Any hay which is thrown loose in the cage which they can play in, run through, pee on, of course eat, is not wasted. Theyve has their fun and usage of it. You are going to throw a lot of hay away though.
As mine live in my shed, I have to use disposable bedding and hay. I have four boys. There is the odd time when I can go in there and the shed is filled with testosterone but usually it’s fine and smells don’t seem to stick to disposable bedding quite so much. Wet areas of bedding and hay are removed every day but a full cage clean is once a week.