according to motorsport italy, rumors have been circulating in the paddock since the japanese gp that lewis is using braking components from Carbon Industrie, the company that supplied for mercedes during his time there. charles, on the other hand, still had brembo braking components, with brembo being the official supplier for ferrari for many years already.
neither ferrari nor the company have ever confirmed this rumour, but charles' comments seem to fit this scenario. the "solution" charles referred to, which is already present on lewis' car, could indeed involve a different supply of brake discs.
[charles mentioned in many interviews that he'd go to lewis' direction from next race onwards]