I finally see the whole plant photos, thank you
From the looks of it, I think it maybe just natural leaf dying off, I see it is the lower leaves having those issues. It is still a fairly new plant, now having to adjust with seasonal light level changes, so be very careful you do not overwater.
Thanks for showing the root zone area, I think it still looks good.
I do hope after watering and excess water drains out, you can position the plant on a table so it can "see" more of the light coming from the window.
Do you augment your light source with growlights?