You are not going to like my answer. I test daily, unless I am not home then when ever I get back home. Phosphates and Nitrates get dosed daily to the exact amount I want them at, p at 0.08 - 0.1, n at 20ppm. Most mushrooms are at the same par level, some tiny deviation as some are under the light some are to the side. Not a significant difference.
Of course - as the saying goes, life finds a way. But I don't believe floating is the way to do that. Mushrooms walk when they want to find a new spot. There's something to be said about foot health, if a mushroom lets go, I believe something deeper is going on.
Thanks Jesse for the words of wisdom