When did the two employees leave their previous jobs?
Sometime in May/early june 16 I understand.
1 You could ask the new employees for their final payslip from their old jobs which will have earnings to date on it.
2 If they don't have those, then they should each call their former employer and ask for the pay and tax details which have or will be reported to HMRC.
3 The employees could call HMRC for the P45 figures every day until HMRC have received them from HMRC. Under RTI, that should be pretty soon after they left but some employers are still having trouble complying with RTI.
I hope this helps but let me know if you have any further questions.