Running the tank for a week is not cycling...you need to be adding a source of ammonia for a fishless cycle.
You're now doing a fish in cycle, and you really need to be testing the water every day, as ammonia can build up very quickly. Either buy your own test kits (and don't let the LFS say they're 'fine'; get them to write down the actual numbers, 'fine' is of no use to us whatsoever) or change 50% of the water every day.
We do have an 'Old World Ciclids' sub-forum where all the Rift valley experts hang our; you'll probably do better asking there, but you do need to do something now or you'll have dead fish very, very soon. They may be small right now, but like all animals, fish do most of their growing in the first few weeks or months of life; many can grow an inch a month, easily.
If your water is that soft, maybe you'd be better off looking at soft water fish; changing hardness and pH is not really for beginner;s, although going from sort to hard is a lot easier than going from hard to soft, it's still etter to match your fish to the water, rather than the other way around.