RFE text received, EAD delyed, Want to know the Timeline after this.

[OceansNwaves]

Joint Filing Spouse GC by USC Wife
23/08 filed
29/08 Received
10/09 Biometrics Notice
20/09 Biometrics Done.
23/09 Received text USCIS RFE
??/?? EAD
??/?? AOS
??/GC
Does any one know what kinda RFE would it be, How do we send the requested info to USCIS(FEDEX/UPS), Guessing it would be Income Proof, as my wife recently got a job. She was not employed at the time of filing.