here is my theory on how that happened.
two days before you had 5 eggs: you collected two eggs that were layed in the morning. because of summer coming and warmer weather and just various thing lining up right, both of the chickens had a short cycle and layed a second egg that evening.
The day before the 5 eggs: you maybe only collected two eggs that were both actually layed the evening before (your chickens did not yet lay for the day.)
Later in the day they both lay eggs
The day you collected five: both hens managed to lay an egg before you came to collect, one of those hens was still experianceing weirdness with her cycle and actually released a second egg yolk with the last one, her body did the usual albumin and membrane, but because she already layed today, that particular egg did not get a shell put on it properly. She also layed this rubber egg before you collected.
Likely tommorrow you will be back to only one or two eggs.