What should ı do for these brown spots? Ph is ok,...

If these are a previous damage and you've corrected the problem and more leaves aren't being affected then you're all good. You can leave them, or you can remove them. Ive heard of removing leaves with damage because they may be holding excess nutrients inside of them....if this is true the leaves may stay the same or deteriorate on their own and release whatever they contain into the surviving plant. Overall the plants looking pretty solid, keep up the strong and healthy. ✌️

I agree to your phosphorus def. the damage is done , and leaves will not recover. but we can stop it.You got to take care of the roots of the PLant. Think over your watering habits, 2 liters sounds like a very high number of water for one plant in 24 hours. Watch your PH. Phosphorus is absorbet around 6.2 PH. And as you already do give her some Phosphorus fertiliser. As i said the dmage wont heal but you an stop it. Happy growing