Greetings, esteemed botanists ans citrus specialists, please share your wisdom and help me keep this little citrus alive. I bought it some weeks ago from an exotic plants shop, I watered it carefully so it wont get overwatered. I placed it at the window for maximum light (not so much since it's winter here). The house temperature is around 20-25 degrees Celsius (77 Fahrenheit). Sadly, last week I noticed some leaves drying and falling. Looking at them closely found that they have some black areas, searched the internet but couldn't find much, so thats why I came here to you, for advice. I am posting photos, hope they are good enough.