Leaf decay from top
This is a picture of a leaf from a newly transplanted sans (~ a week ago). I bought the plant couple weeks ago and divided the rhizomes into 4 different pots using cactus mix soil. I watered the plants a little after potting and they have been sitting near a floor lamp for about 8 hours a day in a warm room.
Now I see a leaf decaying from top down. Any idea what may be causing this? I read in another thread that watering too much causes decay from the bottom due to root rot. Since bottom part of this one and other leaves are fine, I doubt over watering is the issue. When I bought the plant this same leaf had brown edges on each side, which the lady in the store trimmed with scissors - is that what's killing the leaf? I've thought about cutting this leaf but not sure if it is a good idea since the plant might need leaves to survive the transplant and grow roots (?)
I'd really appreciate any ideas and suggestions to save the plant. I'm worried whatever this is may spread to other leaves...