Another way to clean the leather is to mix 20% bleach with 80% water and a small amount of detergent in a container. Stir it up and put a wash cloth awash in the solution then squeeze it out, then wipe the leather with the wash cloth. Don't let the solution to stay wet on the leather. Wipe it...
Simply mix two part water or three parts vinegar, pour into a spray bottle, shake well, squirt on the unsuspecting mold, and clean away after an hour or so.
I extremely recommend the tee tree oil mix. I sprayed curtains and walls with the tea tree oil mix in the afternoon and by that night the moldy smell that had been plaguing our bedroom for a few months already has disappeared considerably.