Growing Things: Diagnose issues to protect plants for harmful insects, blossom end rot

Q: I have recently noticed that I have some sort of issue with my sansevieria — both mother-in-law’s tongue and sword plant, which has also possibly affected a dracaena and my hoya plant. I am considering just throwing out some of the plants if that is what it takes to keep it from spreading.I realize as I look at the photos that the issue may be the little scale-like things I see on the pot, but they remind me more of slugs or something similar, which is very odd. Do you have any id