Here's an idea for disharmony within: have one of your MC's (#1) change the primary vendor they get their supplies from. The new vendor delivers lower quality food at higher prices, but the MC insists on using them. The other MC (#2) can discover that there's something irregular about the relationship between the vendor and #1...perhaps a relative runs it, or the vendor has something dirty on #1. You could also have a staff member be compromised by the external character, and forced to sabotage the business from within, or simply supply information on the owners. For instance, a wedding catering job could be interrupted by a sabotaged vehicle, when it's too late to do anything about it.