It’s very likely that you shouldn’t be converting to CMYK in the first place.
Most labs use printers that do the conversion of RGB to CMYK in their own printer’s software/Rip (Epson, HP, Fuji, etc.).
Sending in a CMYK file that the printer software converts again to print CMYK becomes a very dull ugly mess.
Unless you are sending your file to a large commercial offset printer (which requires a CMYK file to create color separations), send a RGB file.

Chuck