mushroom coral are symbiotic, they do have zooxanthellae.
however many corals will come in many different colors.
those yellow polyps might have been unhealthy, and your adjustment brought them back to healthy state and color. brown is a normal color for Zoanthids. as for the mushrooms/ricordeas they typically are very colorful, and in in unhealthy state the color will fade to white.
see how it works..
healthy coral will have color, that color could be brown, purple, green, or blue.
as the health declines, the color "fades" and it turns lighter.
these are extremely general statements, there are many variable in determining the corals health, but hopefully this might give you an idea of whats going on. while i cant say for sure that they are improving, if you have pictures of before and after, that might help us.
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