From Oval Holes to Semi-Oval Holes

Photo date: February 10, 2021. Photographer: Mark Mahin.   

I took the photos below while photographing only ordinary drops of pure, clean water falling in front of a black featureless background.  On this day I first got (in almost all of hundreds of consecutive photos) orbs with oval holes, as shown below.

Then the oval hole pattern turned gradually into a pattern of semi-oval holes, as shown below (the pattern persisting through hundreds of additional photos).