Since it is your first year, I would guess what you meant, was that they settled on the same overall design.
If they did an online research and found a popular “meta” design, like 448X complex tray, then there is nothing wrong with them following it, even if limited set of parts forces them to use very similar technical solutions.
What you want to encourage them, though, is to work in cooperation with each other and test different ideas on each robot. For example, 169 teams, mentioned above, who are a local powerhouse, all come to early competitions with completely different subsystems to figure out what works the best. As the season progresses they narrow their choices down to the most effective designs. And similar design convergence happens within regions and large alliances all the time.
What may look like very similar robots to the outside observer, may be all variants of a popular “meta” design, but with significant differences in built style and quality on a subsystem level. Even two screw-by-screw identical robots may end up performing in the top and bottom of the rankings if the quality of the build/aligning procedures and program tuning of the clone did not match that of the original design.
On the other hand, you can build two robots with essentially the same set of technical solutions, mechanical and programming tricks, but make them look very different to the casual observer.
The subject of design convergence, robot identity, and clones have been discussed on many occasions in the past.
Design Award and Original Ideas
Two different teams with identical robots
Identical robot designs from same school/club
UNOFFICIAL: <R1> Identity of the robot
Answered: Same Robot Clarification
Answered: Design Convergene issue within a School