How may eggs has she laid and what did the first eggs look like? Photos or earlier eggs and the two white ones could really help.
A BA's eggs should be base white. She lays down the shell first. This base is generally white. In the last half hour or so in the shell gland after the white eggshell has been laid down she adds a layer of brown pigment on top. So you should get an egg that is white on the inside if you crack it but brown on the outside. That brown can be washed/rubbed off if you work at it a bit.
If the egg is laid early before she has a chance to put that layer of brown pigment on it the egg will look white. That can happen to a hen that has been laying brown eggs for years. Often it has to do with some type of surprise or stress, maybe she thought a predator was around or there was some type of perceived threat. It is kind of unusual for that to happen two days in a row but stranger things have happened.
With pullets that have just started to lay you can get strange eggs. It may take a while for them to work the kinks out of their internal egg making factory when they first start. Those kinks might be how the egg is put together or could be how to lay it. It is a little strange that she would get it right to start with and then change a couple of weeks later but again stranger things have happened. This is what I suspect.
The egg is good to eat. I don't think you need any supplements. Her body creates those brown pigments, it is not anything specific that she eats. I'd not worry about it unless you see some other problem and she seems healthy. It's just one of those things that can possibly happen when you keep chickens.
