I also managed to have multiple medium pouches in my inv, when i filled one with p ess the other pouches seem to be connected to that one and have status of filled.
Also if your pouch gets damaged and you drop it to get new one fresh pouch will degrade after first sometimes second time after filling.
EDITED: excuse mua.. NEVERMIND! Just realised i can repair the damaged pouches at Dark Mage in the Abyss
I wasn't really runecrafting much so forgive me!