Re: Substrate in drainage layer
If the fallen substrate isn't actively wicking water up to the plants' substrate, it might not be too big a deal.
If the fabric is actively decomposing, though, now might be the time for a redo, before that breakdown gets worse.
Curious: what kind of substrate turns to 'mud' when it gets below the barrier?
I think I could turn and live with animals, they are so placid and self-contain'd.