Is this mealies or something else?

I am possibly losing my mind. I found a Mealie bug on one plant in the room. I cut it off and quarantined it immediately

I checked the other plants which are all showing no signs. However, they do have this white substance in the soil. It feels hard and like small balls of chalk. Almost like dust.

Thankfully these plants are separated from the others but they seriously don’t show any signs of infestation. I don’t know if this is just chalk or something in the soil or if it’s part of it. If it is then four plants have got to go!

Watering habits are when needed. They are in a window with no direct sunlight on them but enough sun