Hermits are not much good for anything IMO. Sorry to hear about the puffer. I couldn't pull up that link.
If the puffer had ich, then likely your tank will soon get it.
Take a look at the Diseased Fish Thread at the top of this forum and the pics there of fish with ich to see if that is the problem you had. If so, then you will need to treat the remaining fish. Read the post on ICH in the FAQ Thread.