Is there a change of the nutrients found in cucumbers when they are picked green from when they turn yellow if not used right away, and are they safe to eat after they turn yellow?
Certified GKH Gardening Expert
It has definitely undergone some nutrient change, but this is not harmful. This is natural for it to turn yellow once it is over-mature. They are still safe to eat, but the seeds will be fully mature, and no longer soft. You could still use the cucumber but save the seeds for planting.
Here is an article for more information: https://www.gardeningknowhow.com/edible/vegetables/cucumber/when-to-pick-a-cucumber-how-to-prevent-yellow-cucumbers.htm