Hi
@twigsnberries
How old are the hens that are laying these eggs?
What type of feed do you provide?
There are many factors that impact the quality of eggs - age, nutritional/vitamin deficiency, disease, ventilation and on it goes. Since it's random, it could be age related if they are different ages - also free ranging, maybe these certain girls are eating something that the others aren't(?)
The only thing I can think of, is to provide some poultry vitamins a couple of times a week in the water and watch to see if those girls are eating a specific plant?
Here's some information on egg quality
http://www.thepoultrysite.com/publications/1/egg-quality-handbook/
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/