Beginner Gardening: Rex Begonia help... spots on leaves... , 0 by JennieV

JennieV wrote:
I have been collecting some rex begonias since the beginning of spring. They have been doing well all year so far except for the last few weeks when one of them started to get these spots on its leaves, it has spread to a few other plants since then and I am afraid that they are all going to end up getting it and I am going to lose them all.

I have them all in the house, west and east facing windows. No direct sunlight, and I have them on pebble trays. I live in Southwestern Ontario, Canada. I have stopped watering them as much as I was in the summer when I noticed that my plants were getting these spots, thinking that I could be overwatering for the time of year possibly? One plant has brown spots on it and the other one has what I think is powdery mildew and the spots as well. I have tried looking it up on the internet but I am not 100% sure of what it could be.

I went out to the local nursery where I had got most of my begonias and brought a few of the leaves to show them and see what they would recommend. They recommended Safers Ready to use Defender garden fungicide. I tested it out on one plant because I am not sure if I should be using a garden fungicide on a houseplant? Nothing seems to be happening. I would prefer to use a natural home remedy if at all possible.

If anyone could help me identify what the problem is with my beloved plants so I can get them better it would be greatly appreciated.