Monstera albo is rotting?

Hello! I have had this monstera albo for almost 2 years. It was growing slowly and it never gave my any problems until now.

Two or three weeks ago I noticed that some leaves were browning. I checked the pot and saw that the roots were coming out of the pot holes so I repotted. The new pot is a bit bigger (17cm and the old one was 15cm).

Now I noticed that the stem is browning too… The new leafs are the ones that are browning, the old ones look better. Even the newest leaf is browning. Should I cut??? 😭

I didn’t have sphagnum moss to get the perfect soil mix and I don’t know if that might be part of the problem… i just ordered some but I don’t know if I should repot again. I repotted the 20 of September and is now October 2.

Also it seems like the monstera it’s not holding properly to the new soil. What should I do? I’m really afraid of losing this plant… it’s one of my favorites 😔