Seeing that you have been around quite some time here, I will avoid the obvious newbie questions.
My opinion is as follows;; chickens do take breaks from laying. Your chickens are at middle age period. That translates to reduced egg production. Covid period is just a coincidence in time.
Placing placebo eggs into nest boxes will not stimulate egg production. It is only effective at teaching young pullets house manners.
Your location is not in your profile, I just assume you live in the northern hemisphere, where days are getting longer during Spring time. If you live lets say in Australia, or such, then days are short, and winter approaching. That would also be most common factor there at this time.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
