Review of FHIR R5 and R4b indicates that the base Condition resource does not include the elements dueTo and occurredFollowing. QI-Core can include those elements if and when they are added to the base resource (e.g., with R5 if added). The issue of condition cause is not captured in the Condition resource. With respect to occurredFollowing, that concept might be captured more as a query expression seeking onset timing of different conditions, or timing related to other events or triggers.