Hello ! You don't need to panic , the down leaf is probably dropping down because of a shock on her stem as she's the only one like that we ca assume that it is not a def/exces or a disease. On the upper leaf the edges are begining to curl and it's generaly due to heat but you temps is around 25°C so I can't really say what it is !! Hope it will help you 😁👍
Double check your pH. I've had leaves edges curling up due to high pH. Also, 1 liter of water a day is too much for a plant that size, over watering can be the cause too, try 100 to 150 cc per day.