Some advice please on the best way to go down the CEDR route. Does it need two claims because the PNR was split? Trip previously briefly mentioned upthread.

JER(J)-LHR(F)-JFK(F)-DCA. 2 pax BAH booking.
Inbound aircraft from LHR to JER to start our main journey was delayed. Part of this was ATC but part BA - the aircraft arrived at the LHR gate 30 minutes late from its previous destination due to ATC but was not ready to depart for another 68 mins due to late arriving aircrew and delayed assistance for a disembarking passenger - my understanding is BA allows 35 minutes for an A319 turnaround so that means 33 'countable' minutes of the delay is due to BA. (We were on this aircraft on a separate PNR so I am confident about timings and the Captain's announcment detailing the reason for the delay)
The delayed departure from JER at the start of the main BAH trip due to the late inbound made us 104 minutes late in to LHR which meant we missed our connection, including a possible rebooking onto the last direct IAD flight of the day. Eventually re-routed via BOS to DCA - arrived 7 hours late. One of us downgraded to J to BOS so PNR was split. Both of us downgraded to Y on BOS-DCA.

BA have paid only £450 for the downgrade, based on 75% of TATL and 30% US sector base fares - so low because they have excluded the £450 YQ.
They denied any late arrival compensation on the grounds that the majority of the delay was caused by weather and ATC. However, we missed T-35 conformance for the last IAD flight by only a few minutes - even 10 minutes earlier and we would have been fine. I have argued that if the 33 minutes that were under BA's control had not been lost we would have made the connection and arrived close to on time. Still no joy and I now have a deadlock letter.

The two PNR claims are slightly different in that one has the TATL downgrade and I want to claim for the YQ as well as delay. The downgraded pax was linked to the new PNR. Should I make a single CEDR claim under the new PNR with a note at the end asking for the other PNR to be added or will a claim for both of us using the original PNR give CEDR all the details they need?