what are the greens you are feeding? Some greens actually reduce nutrients by interfering with absorption in the gut, if I recall, they can bind with some nutrients. I have one hen that prefers greens to other foods. Her shells are thinner than the other eggs, and the whites are very watery. She chooses to eat less of the feed and do more foraging than the other hen.
Some very nutritious veggies are among these. The best way to break down the problem chemical is by cooking. This is the case with beans, for example. There are studies on just about anything you might consider feeding, and some on things you would never think about! I read about everything on Google scholar. I would search it using the keywords: poultry, chicken, feed, and whatever plant item I was researching. Typically what happened was most foods were fine up to a percentage of total feed for the day. (Usually 25% or so). After that the test chickens would start to show a deficit by losing weight and laying problems. Keep in mind the testing has production birds in mind, and is focused on cheapest readily accessible or waste products that get best results.
For example, sweet potato leaves and mulberry leaves are good, while bean leaves are not... But that would just mean you could feed more sweet potato and mulberry leaves while a very small amount of bean leaves would be okay. (Not ornamental sweet potato! The ones that grow the real potato). The birds still need the correct amino acids from proteins and all the other nutrients. If you can take the time one day to just sit and observe what your chickens eat you can know how best to deal with their diets. I never saw anything that was used at more than 50% except for corn, (hard info to find, but many manufactured feeds are 60% corn or more) but that much corn is too much in my opinion.
Another issue I did not see addressed by others was the possibility of worms... If you can borrow a microscope or find one used, you could check their poop. Intestinal parasites suck up the nutrients the birds should be getting from their food. Pumpkin seeds are supposed to help keep them under control.
I am betting, however, that by the time you read this, your hens eggs will be getting normal. It most likely is just a new layer issue.