All the PCNs are sitting at £35 at the moment, which is frankly a bit odd.
I suggest you contact Days and ask them if they've appealed the PCNs on the hire company ground. If they have, ask if they've received a Notice of Acceptance or some other correspondence confirming liability has been transferred.
If Days have not taken any action yet, instruct them to challenge all three PCNs on the hire company ground, requesting that liability be transferred to the leasee.
Please report back urgently, whatever the situation is there will be follow-up actions for you.