I think it’s because you give to much water.
You’re not giving any nutrients so that couldn’t be the reason.
Do you have drainage holes in the bottom of your pot?
Only give water when she’s dry.
(I would give 0.5L every 2 to 3 days when I look at your plant)
It could also be that you bought heavy furtilized soil or soil with the wrong PH (ph needs to be between 6-7)
But your plant looks healthy.. as long as your new growth is nice and green you don’t have real problems.
Next time fill in more info (day temp - how much water you give - how big is your container - how tall is the plant) when you do this it’s easier to know what’s wrong.
Good luck!