Dear Sharlene and the tranzed class,
Thanks for taking the time to update us about your tranzed class. I just stumbled upon this thread and it makes me feel good to know that you guys have tanks up and running and are supporting such a project. It's not always easy and it takes effort, so keep up the good work.
As far as the chocolate chip starfish dying, they are very sensitive to changes in salinity. One time I was trying to increase my salinity and did a water change with water of a much higher salinity. My chocolate chip starfish was the only thing that got affected and died. Everything else was fine. However that is not to say that is why mine died, as there's no way to be certain.
As far as videos to watch, I think these videos will help your students develop a grand plan to tackle tank maintenance, as that will be a key part of your future success.
When in YouTube, search this: How to Reef Aquarium Maintenance Part 1 Introduction.
The videos are by a guy named newyorksteelo. He is positive and educational and can be a stepping stone into learning more about reef aquariums for your students. Don't worry he is not negative.
If you need any more help feel free to ask.