Disease in which the roots of the plants rot. This is caused by overwatering or fungal/ bacterial.
Try adding charcoal, fungicide and/or bactericide to your soil- this prevents bacterial and fungal infections from attacking your plant
Add or increase Drainage- planters with draining holes
Water when topsoil feels dry- Simply put your finger 1 inch into the soil to feel for moisture, or use a moisture meter. If you have a drainage tray, make sure it’s either dry or not directly touching the planter (you could add a few rocks to the tray to make a separation).