brown spots, yellow leaves, gray leaves ?

You are likely dealing with root rot. I’ve only experienced root rot twice and both time was on house plants that came with horrible soil. The first time I took the plant out of its container and cut away and brown mushy roots. Then replanted it into new soil. This plant did great after that. Second I was lazy and used hydrogen peroxide mix at a rate of 1 part H202 / 3 part water. Drenched the soil with it. I feel like it helped but that plant never fully recovered. You could try a repot if you can with good soil and cut away the dead root. Or you could possibly try the H202 drench. Hope this helps.

Same as last time. Root issues, Likely getting a bit of rot and lacking in oxygen. Control your watering habits more and I'd also say amend more perlite into the mix next time but it looks like it has a lot. It can also do this from root damage like an aggressive topdressing, Good Luck!