Julie,
You might now understand the reason I usually start off most of my Geryi post with the sentence "Geryi are notorious for not acclimating as well as some other uromastyx species".
I agree with your logic of not jumping into another group until you can determine what may have gone wrong with the first group.
One of the reasons Geryi take longer to acclimate is because of their unwillingness to eat after shipping. The fact that your geryi started eating and you did not mention any signs of illness, leads me to believe that you may need to take a closer look at the enclosure, temperatures, and other husbandry issues before disease.
Did you separate the uromastyx upon arrival? How soon after you received them did they begin to go downhill? What were the signs (other than not eating) and symptoms? Was a vet consulted and if so, what were the findings? Did you consult a vet for a cause of death? What led you (symptoms) to de-worm them and what was used? What led you to administer antibiotics and what was used?
One big thing I have learned with geryi is that because of their slow acclimation, it is imperative that outside stress, movements, and handling are minimized until they have adjusted. If ‘I’ have a geryi that does eat for a week but everything else look fine, I am not concerned. I almost expect this in adult males. I do not try to medicate during this time unless I see very apparent signs of illness. If I do see urgent signs (coccidia, respiratory) I immediately take the animal to my vet. If you try to guess with parasite medication or antibiotics and the only problem is stress to begin with, you are sending the animal on a downward spiral towards a crash and burn situation. Sometimes time (with the proper environment) is the most beneficial preventative medication you can give.
There are probably a hundred more questions I could ask in order to try to narrow down the problem or problems. It might be a better idea if you could post some additional details regarding the enclosure setup, symptoms….ect