Problem. Certain Plants Have Got Disease Which Is Spreading To Other Plants.

Question

Brown blotches and the dying.

Answer 1

Without more information or what kind of plants, I can give you some possibilities. Consider your watering practices. Overwatering is a common problem. Here is more:

https://www.gardeningknowhow.com/plant-problems/disease/plant-leaf-spots.htm

https://www.gardeningknowhow.com/houseplants/hpgen/desperate-houseplants-dealing-with-common-houseplant-diseases.htm

https://www.gardeningknowhow.com/plant-problems/disease/leaf-browning-in-center.htm

https://www.gardeningknowhow.com/edible/vegetables/vgen/brown-leaves-on-vegetables.htm

https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm

https://www.gardeningknowhow.com/plant-problems/pests/insects