ehh, underwatering is more of a droop, like your plants been running in a desert all day and just wants to collapse.

Your plant stems are very, very, very red. If anything only your fan leaf top part of the branches could show red color, but the main stem and the whole plant looks red, the burns have yellowing around some but most it looks like the leaf just died. I have no idea what this is, outdoors = less control. Red stems i understood as the plant storing food in excess, and that it is looking for more of somthing else. more info