It is not only theoretically possible, but it also very likely if you consider:
1) that these same runners after 1993 World Championships had become international celebrities, and thus didn't have to rely on overachieving for their livelihoods.
2) that these same runners who took nearly a full decade to achieve what they did had now matured into women. Don't you think that becoming interested in men would tend to work against maintaining the same level of training load, intensity, etc, especially when your coach dictates such matters for you?
3) that it was widely reported that Qu, the second biggest star on the squad left Ma due to such conflicts about having boyfriends, growing her hair, etc.
4) later it was revealed that most of Ma's Army had disbanded as a result of their great level of dissatisfaction.
Obviously, any criticism that these athletes "failed" to produce similar results must take such factors into consideration. Under the circumstances, it would have been nearly impossible even for drug cheats to replicate these feats.
I think I am repeating myself to no avail, but I need to emphasize again that too many people have an unwarranted presumption that forces them to accuse the Chinese of being drugged. Of course I would never deny that they certainly used substances that enhanced their performance and endurance capacity, and probably their recovery rate. But this in no way suggests that they used a BANNED SUBSTANCE!
So, all this talk of cheating is absolute nonsense, unless you can prove that ALL substances capable of enhancing performance are on the list of BANNED SUBSTANCES. And this is of course impossible everywhere, and even more so in China, where they have an entirely different medical discipline than the allopathic one.
It is undeniable that certain plant substances often have greater or comparable efficacy when compared with drugs. For instance, there are studies that show that turmeric is as effective in reducing pain as cortisone, and of course without any side-effects. This is one of hundreds of examples.