With a nation of two hundred people, if there were one hundred family units, each with two kids, that would increase the number to four hundred. After one generation. I won't calculate it all out, but maybe you could look at the time it takes for a 'world' to grow out of two hundred people and use that as your time frame?
The more the population increases the faster the rate of growth increases. Naturally, as more people are in the world, there will be more people studying the sciences and stuff. But if that takes too long, perhaps you could have a competition between rival scientists to develop the DNA robots.
And if they have solar and nano technology, it's safe to say that they
could develop DNA robots, however, they are completely alone, so even if that would have been easy on another planet with a huge group of scientists, they have only a few...so naturally it takes them a few hundred years.
Thus, you could have a timeline like this:
0: Ship arrives with solar and nano tech.
100: As colony expands (maybe four generations later) the guy comes as a prophet and splits them.
100-500: Series of wars and population growth slows because of the wars. But at this point you've still only got a population of thousands, I think.
600: Both rival sides develop, within a few years of each other, DNA robots
Wait a minute, you just totally changed the plot at the end there.

So they've had DNA robots for a long time? Or they've been a secret of one family? I didn't get your change of plot at the end.