"They tend to be hard to keep for any extended period of time in a lot of cases. They exhibit the same symptoms as yours, heavy breathing, loss of appetite, and sooner or later loss of color. Then just lying out in the open on the gravel or in a corner and whithering away to nothing."
By "they," do you mean BlueDot Puffers or just fish in general. And luckily he did not lie out in the open withering away, my family said he was still swimming today. They said he actually did eat a couple flakes today too, which he hadn't done the last week.
And I know someone's going to jump on that now, so I'll just say in advance: No, the puffer's diet did not consist only of flakes. I gave him flakes, pellets, krill shrimp, and he ate many snails in that tank too.