How to Reference three authors and their papers in a stretch Scenario:

My own version: The authors in [5,6,7] focused on the problems associated with the production of X.

[5] ABC et al 2018

[6] DEF et al 2018

[7] GHI et al 2019

A corrected version from editorial production team:

ABC and Co-workers [5,6,7] focused on the problems associated with the production of X.

Question: Can one say: ABC et al, DEF et al. and GHI et al. [5,6,7] focused on the problems associated with the production of X?
You should check with the typesetters/publication team for their style guide and make sure they realize that 5, 6, 7 are different groups if that is the case. Clearly the version they rewrote assumes they are from the same group. That might still be appropriate if the author lists differ but the senior author/laboratory is consistent.

Your last example is fine, but may or may not comport to their preferred style.