Hi,
Please refer the below link:
Experiencing Adobe Experience Manager - Day CQ: AEM 61 - Touch UI Composite Multifield with Rich Tex...
It has a brief description on how to create a composite multifield component with rich-text inside it (in AEM 6.1).
The above link also has a demo package. We've tested the above package in AEM 6.1 and it is working as expected for us. Could you please take a look at the package as it might help you in debugging your issue. If you still see the same issue, please let us know. We'll be more than happy to help you!
Hope this helps!
Regards,
TechAspect Solutions