[smokinreefer]

Yes, thanks for the pictures!!! They actually are quite helpful.

It sounds like maybe you need to look for another one of these nice white toadstools that you were lucky enough to find. Since under your care it'll turn into a true yellow toadstool. And then when it's back to its true yellow form, do some testing and logging of parameters. If it eventually darkens up again, do some more testing and logging and compare them from the earlier results.

I'm thinking that maybe a way to sustain the bright yellow would be a low nutrient high light environment?