
It could be root rot or sunburn, root rot is when you over water your plants and the roots suffocate in the water, if you light the plant out of the pot and it’s dripping wet or if you see mushy black roots then it’s root rot, sunburn is just because those types of plants don’t like direct light, they live better in indirect light
If it comes down to it you can always chop and prop, you just look on the stem for a node (the little brown bumps ) and cut like half an inch below them, and then you put it in water to start growing. Then if you want to put it back in the dirt you can or they survive in the water
You should take all the dead leaves to promote new growth and then you should try to bottom water, idk if you already do it but basically its filling up a little container with water and then placing the pot in the water so the soil will slowly soak up the water. When you water from the top it wont fully soak everything because water is lazy and will find an easy way out. Also does the pot you have have holes at the bottom or is a decor pot and then a plastic one on the inside ?