What they are eating is not adequate nutrition for breeding or for pet birds. Seeds do have nutrients, but most seeds are no longer fresh by the time they make it to the shelf and have lost most or all of their nutrients. Any added vitamins are lost when the bird hulls the seeds. The solution to this is to offer a nutritionally balanced diet such as pellets or our foraging diets – Nutri-Berries and Avi-Cakes. Pellets also contain seeds and grains, but everything is ground up and formed into a pellet so that it is nutritionally balanced. Our Nutri-Berries and Avi-Cakes are nutritionally balanced the same as a pellets, but they are not ground up. They contain locally grown, fresh, hulled seeds with other ingredients to result in 100% nutrition. Cockatiels do very well on these foods because it satisfies their desire for seeds and also offers important foraging exercise. The carrot greens have probably helped your birds so that they are not completely malnourished.
So you need to change their main diet. In addition, you should offer chopped fruits and veggies, dark leafy greens, multi grain bread, and while she is laying eggs and if they hatch chicks, she should have some cooked eggs with the shell cooked with them. Wash the outside of the shell thoroughly before you break it and cook them. Since they do like the carrot greens, they might do well with some of the leafy greens. You might also try broccoli florets. They may or may not eat fruits. The veggies, greens and cooked eggs are more important. Laying eggs is hard on a hen, and her health will be fragile if you can’t get her to start eating better. The cooked eggs and eggshell will provide protein and calcium she badly needs right now. A cuttlebone would also be good for her.
I’ll give you the link to our feeding guide and I also recommend you do as much research as possible on how to breed cockatiels, so that you can be ready if they fail. Given his young age, these eggs are more likely to be infertile and since you need to work on their nutrition, this would be for the best. I would be concerned for her healthy right now, and more so if any chicks hatch. Luckily breeding birds tend to be more adventurous eaters so if she will start eating a good diet right away, it will begin to help her very quickly. If converting her to a nutritious food isn’t going well, then at least get a good bird vitamin to put in their water until they are eating better. Also, if they do hatch chicks, the parents will eat several times more food than before and you may have to replenish it a few times a day.
Bird Food Guide
Thanks for the update and good luck with their diet and everything else!