Err no that didn't come out right. I was refering to the fact that they are making clones of clones of clones of.. you get the idea. It's basically the same problem that a species like the Asguard had in SG1 - thyey were highly advanced but over milenia they lost their original blueprints and began suffering from DNA errors.
The Jem hadar as a species would need to refer back to their roots every now and again because they would become vunerable to specific things - if all the clones were identical then they could all be alergic too / susceptible too / suffer from EXACTLY the same thing. THat would be a huge tactical error on the part of the founders! WHile they sare skilled genetic manipulators - cutting and pruning and designing is one thing, but if you take cuttings from only one tree you'll just get the same tree, they would need a supply of fresh DNA of a living and evolving species. Perhaps they have actually bred true species of jem hadar they don't use for war, that can breed and that they can actually experiment on (testing them for disease resistance etc) - which in turn would lead for a very 'moral dilema' led issue - do you interfere or not, especially if you discover it AFTER peace has already been sued for!