That’s not super unusual for Elemental Chests for some players, from what I’ve seen, but it’s definitely very unusual for someone who’s regularly skipping Chests.
I only speed up Raid Chests, and routinely get Elemental Chests around 9-10 days apart on average. (My log is here.)
I doubt they’ll tell you anything other than a generic answer initially, but I think it’s worth contacting Support and asking if they can investigate their logs to understand if there might be a bug or other issue, since the frequency seems to have changed despite other factors staying the same.