I find it ridiculous that the EC is reasponsible for unapproved (or even unknown alterations) as it just encoureges people to make alteration without approval knowing that if anything goes wrong the EC pick up the bill.
OP I’d be inclined for the EC to remove the downlights and restore unit to it’s origional lighting configuration to deter this happening again.
What about passing a bylaws stateing ALL alterations done without EC approval will be removed at owners the expence unless ower accepts reasponsibility for the maintenance of said alteration. Surely if you can put limits on one item (downlights) why not put limits on ALL alterations.