You say you have multiple layers of fleece Brittany, this might be your problem. Fleece should wick moisture through if it is a single layer with an absorbent layer behind. If you have fleece on top of fleece you prevent it from working properly (I should say here, whilst I have only had my guinea pigs for a little while, I used cloth nappies with fleece as a liner for years with my human babies so well practiced with the principles of fleece!). In terms of prepping, providing you have 100% polyester fleece (just ordinary stuff you get in cheap blankets or from craft stores) and you have washed it a few times with detergent, and crucially, no fabric softener, then it should work fine.
Currently I am using a layer of fleece with a mattress protector beneath (needs to be either cotton, bamboo, hemp or a product called zorb to act as your absorbent layer, anything that is polyester based won't work)
I find that the fleece is dry, the protector is wet, as is the correx beneath if the wee is fresh. I wipe away any wee stains morning and evening from the correx with hot water and vinegar. So far the piggies are odour free, although on the day of twice weekly fleece change it smells in the corners where they tend to go but I only notice it as it is near my face as I shake off the hay.
If your boys only pee in certain areas, such as under their hay rack, it may be a good idea to put smaller towels and fleece patches under the rack. Then you will only need to wash and replace the smaller pieces of fleece and towels instead of the whole lot. But if they do indeed pee everywhere, there is not much else you can do but replace the whole liners. Are all four of your boys in one cage? Splitting them into pairs in larger cages may work out better for you.
