I planted a couple of lemon seeds in a pot in June 2021 and a baby lemon sprouted. She grew up in a really healthy way. Since then, I have changed the soil and the pot only once. I used regular soil that I got from the supermarket. Unfortunately, lately, I've been having a problem with my baby lemon tree. Since I am not very knowledgeable with botany, I don't know the reason for this and I don't want to do anything wrong.
There are various white and brown spots on her stem. Two of her leaves are starting to turn brown. Also, when I pour water, somethings that look like tiny tiny bugs jump up, but when I don't pour water, there is no movement in the soil. I live in the south of Germany, the sunniest city. No matter how sunny I say, there are many dark, cloudy and gloomy days. I try not to water her too much. She stands in front of the sunniest window. You can see the photos attached.
My baby lemon tree is very precious to me. When I planted her, I wasn't feeling well mentally, I was going through stressful and unhappy days. I don't want to lose her. I hope someone can help me figure it out.
I am looking forward to hearing from you soon.