What's causing brown spots on my succulents?

I've dealt with this on my windowsill plants, and it's almost always one of two things: overwatering or fungal/bacterial rot. Succulents store water in their leaves, so they don't need much - if the soil stays damp, the roots and leaves start breaking down from the inside out, which shows up as those brown mushy spots. Check if the soil is staying wet too long, and if it is, let it dry out completely between waterings and make sure your pot has drainage holes. If the spots are dry and papery instead of mushy, it could be sunscald or a nutrient issue, but wet rot is way more common with these plants.