Please help

Hi!

I am a novice plant keeper, I do not have many, but love the ones I do have. This peace lilly specifically, is very very special to me as it was given to me three years ago when my grandfather passed away.

I have been able to keep it happy and healthy for the last three years, about two months ago, I noticed it was becoming root bound, I had a plant savvy friend help me repot it because I am terrified to kill it. Once it got re-potted it seemed so happy! It bloomed new flowers and was making new leaves. The past few weeks, I started noticing a lot of the leaves yellowing and the ends on some leaves turning black.

These pictures are not the worst of it, as I was told to cut the yellowing leaves off to help the plant preserve its energy. I cut probably four yellow leaves off before I thought to take a picture and ask for help here. I will be so absolutely crushed if this plant dies, any and all advice is welcome.

I water it every 8-10 days or when it starts to look droopy and it is usually kept in indirect sunlight but I do put it in front of my balcony window maybe once or twice a month to get it a little more at times.

(I know this plant is toxic to cats - it is kept in a separate room from them at all times and when I put it by my balcony window it is never left unsupervised)

Thank you in advance 🥺