ok so i'm sure i've determined that a few of my cacti and succulents were in need of some roots. i found an old mans beard had fallen over on its side and where it broke off was right at soil line, which exposed a mushy pile of stem (almost hair gel texture) (but not black, more greenish yellow or pea soup color) and and under that hardly any roots at all. i cut off the mushy rotted part from the main plant that had tipped over, and the rest of it looked healthy, or dehydrated like. not shriveled up or dried up like a apple or grape, more like a sponge looks dried compared to damp. some others, like my donkey's tail, haworthia, and some others have suddenly broken over too, and the bottom leaves near the soil are all dried up shriveled and brownish, like a dead leaf. (not like black rotted tho). their stems were dried up to a crisp. in the soil below that, there's nothing, no roots or anyhting.

am i underwatering, or overwatering, or not enough water when i do water, or too much? its like i'm overwatering and the roots are rotting away and then the plant above the soil ends up drying up because of not enough water cuz suddenly no roots to provide it with?

what do i do?