Small white deposits keep appearing around the roots, and close to the surface of my potted plants. Today I dug up a plant that's dying, and I realised these deposits are stuck around it's roots further deeper in the soil. These are small with a maximum size of about 1cm. They are a bit hard and crunchy when i tried pressing them. They break when I applied some pressure. Can someone tell me what these are, and if they are killing my plants, and if yes, how can I get rid of them?