Potential CPPC arrangement?

I was reviewing the POs that my firm executes with our subcontractors on a Cost-Plus Fixed Fee basis and I became concern that our Sourcing dept is not specifying the fixed fee we negotiated with our SubK and the vendor is simplying invoicing (and we're paying) a fee % of their invoiced cost.

With no mention of a fixed fee amount or NTE amount for fee anywhere on the PO, has my company inadvetrantly slipped into a CPPC arrangement? If so, will a simple admin mod to the PO clearly identifying the fixed fee amount, rectify the problem?

Thanks!