I’m not sure what you mean by a cost recovery notice (recovery of what?) but it’s pretty simple, an OC can’t impose fines for a by-law breach. An OC has to apply to NCAT to impose a penalty for a by-law breach.
So you can ignore whatever these notices are. They can’t charge interest either.
However, a tenant is obliged to comply with the by-laws. The OC can apply to NCAT for the tenant to be fined, presuming they have issued notices to comply. I suggest you tell the tenant to comply or risk a penalty if the OC gets it right.