But they are not C. foai, but C. furcifer.
The foae sibwesa has no yellow in the face, a nearly total black anal fin and a lot of black in the tail an dorsal fin. Your fish looks totally like a C. furcifer sibwesa.
In the actual version of Sigfried Looses (German featherfin expert) book is a picture of a C. furcifer sibwesa that looks like your fish an a photo of a C. foai sibwesa that looks totally different. It also says that the main difference between the two species are the dark fins of the foai.