My African Milk Tree developed brownish black spots on it and the leaves are turning yellow when I brought it indoors. . It is about a year old and was outside for all of the summer and warm weather. I took it in recently when it became too windy outside. It fell on its side, but I picked it up and brought it inside as soon as I noticed. It gets about the same amount of light just not as intense now . I don't know if it is rot or sunburn or something else on it and I don't know why it's leaves are turning yellow and drying up and falling off. If anyone can help me understand what is happening and what to do, it'd be highly appreciated.
I would guess too much water. Light through a window is not the same amount of light as outside. With the decreased light and shorter days, it should probably be watered a lot less. It looks small enough that you can lift it to feel when it seems quite dry before watering it. Someone else will have to say what you can do now. I would stop watering it until it is quite light. That being said, I don't have great success with cacti and succulents (overwatering, I think), so wait till you hear from someone else.
What temperatures has it been exposed to recently, before it was moved inside? Euphorbia are not very cold-resistant.
I agree with mandarin's suggestion. Even if the air temperature was not excessively low the wind chill temperature could be.
