My two female dicrossus are still immature, and thus haven't changed sex.
However, if we look at this from an evolutionary point of view, we can say that dicrossus might have other reasons to change sex than being stuck in a hole. Although it may be that this genus was merely 1st to the punch other fish have had a long time to evolve too.
Heaps and heaps of marine fish change sex, and there is little reason for them to do this on the possibility that the sea might dry up. Most marine fish that do this live in harems and change sex when the dominant male is removed, and the top female changes, almost always within a week.
Great white sharks also change sex irresspective of both the above reasons to do so, and do at a certain time in their lives when they are old anough to be more useful to the species procreatively speaking, when they can have many young. And as we know from whale sharks, which can produce 60 two feet long youngsters, being a big female is a good thing.
Apistos often get stuck in the same kind of puddles as dicrossus, and I have never heard of them changing sex.
So why is it dicrossus? Why is it this one genus of three fish that change sex in the whole cichlid world of ~ 2000? Is it because of the challenges that these 3 species of fish faced that caused them to develop this ability, or is it that one fish (that looks like all of these fish in the genus put together) developed this ability and as such did not die out, but instead was successful enough to develop into three separate species, or was it a blend of the two, which is more unlikely.
So, the reasons for sex changes in any animal are varied, and it is likely that unless there is an outstanding reason for any animal to change sex, it is unlikely that they do.
BTW, to offer my opinion on malawi cichlids having this ability, I would definitely say it is more likely that they were just showing their true colours, so to speak. There is no huge reason for cichlids from malawi to do this