I have two young avocado plants in my room that show some problems.
The older one (I started growing the plant from a seed 4 months ago) started to show yellowish/brown spots on its leaves about a month ago and is loosing these leaves quickly after the spots appear.
The second one I started growing about 3 months ago. It doesn't have these spots but started to grow misshapen leaves and lost some lower leaves as well.
It's summer where I live (Switzerland), so it should be warm enough and they sit next to a bright, southeast facing window. I water them when the top inches of the soil are dry. I also tried to spray their leaves because I thought the air humidity might be too low, but that didn't help either. 4 days ago I then tried to add very little fertiliser to the older plant, but haven't seen any changes to the better either.
Do you know what could cause this? Thanks for the help!