What you are experiencing is a natural stress related reaction. Place them on the substrate, provide good current, make sure your parameters are in check including temp and run your actinics only always on the day of new acquisitions. Just give them time and whatever you do, don't go moving them around. This will not only delay expansion but over time it will stunt their growth.
Though very hardy when it comes to adaptability in new system and to lighting, zoas are at their weakest most vulnerable stage during fragging and in transit/shipping. Even if they are bagged and driven across town to your tank. Not to say that this will kill them, the process is simply stressful as it is with any coral, but they bounce back very quickly. They are the Hulk Hogan of corals. They are very susceptible to slimming and BI when moved for longer periods of time. This is why LFS will experience die off with well packed overnight shipments. I know, I rambled again, LOL.
Other reasons why they may be retracting.
1. If their previous environment was dramatically different then yours, expansion could be delayed.
2. If the alk was dramatically different, it would cause a delayed expansion.
3. Inverts running to check out the new entry into the tank will cause a delay as well.
4. A rough trip from across town, temp shift, different lighting, etc would cause delayed expansion.
5. Nipping fish that are also curious would cause a delay.
6. A predator or host imported on the rock from the previous tank can cause a delay.
Did you dip the rock or place it in a QT? Just curious.
What you stated above is a correct assessment, they are just getting use to your tank.
Hope this helps my friend.
Mucho
