I have a mint plant outdoors in a pot that grew rapidly and then suffered from some insect which just loved eating it. It's in a mostly sunny spot next to a high bed. I sprayed it with a solution of water, liquid soap and canola oil. But later, it looks like the leaves are burnt--not always from the edges but from spots in the middle as well. Could this be the canola oil in the spray? Also wondering if it could be something else.
I let the new growth grow without spraying, but it seems to be affecting new young leaves as well. They turn black and are almost crispy.