I started watering a bit more after noticing the soil just as you thought and I also read somewhere that a lot of heat can damage the roots (I need to change the pots position after like noon because a a coconut tree overshadows all of them when I use to do it I noticed that these pots were like cooking, they were hot to the touch and this was also why i started watering more to keep em cool ) my theory is that since every other pot has two plants and one pot has plants they don't have that except a bit droopiness maybe and this plant is the only plant that is singled out it took a lil damage , idk it's just my uneducated theory tell what you guys think