Not sure about that - you might need to call. Since the QF agents often have a bit of a dearth of skill it might be helpful to ensure you use the correct terminology with them:

you already have separate tickets - assuming you used 16 segments you’ll each have tickets with four ticket numbers.

these tickets are attached to one reservation (often referred to as a PNR) - what you’re looking to do is split the reservation/PNR so they can be modified separately.