STRIPED BURRFISH IN TROUBLE PLEASE HELP

Sorry this post is so long, and I hope you'll read all of it, but if not, here's a summary:
THERE ARE TWO VERY SICK BURRFISH IN MY OCEAN LAB AND I NEED TO KNOW HOW TO TAKE CARE OF THEM



I am in my school's oceanography lab and we have two burrfish. I will describe both of them seperartely, as they are in very different conditions.

Burr Fish #1:
Tank Conditions:
about 10 - 20 gallons, but is part of a 150 gallon system
saltwater
substrate is broken shells on the very top and a lil sand underneath
Fish Conditions:
Its spines look good, but it looks fairly skinny, because its head is large enough but then its stomach indents in
It was doing barrel rolls once? We dont know why
Water quality tests were fine, we cant test alkalinity because we dont have a test for that.
We have been feeding it shrimp by tying a string on the shrimp and hanging it in the tank
We added denitrifiers and bacteria, but it doesnt seem to have done much

Burr Fish #2:
Tank Conditions:
150 gallon tank, shared with; various clownfish, damselfish, and a yellow tanks. and lots of anenomes and algae as well as a starfish and a basket star, which do nothing. and a horseshoe crab.
Fish Conditions:
The fish is about four inches long, and much larger than the other fish in the tank, so shouldnt it be dominant? However, it stays harassed in the corner and looks very distressed as it swims into walls and goes in circles.
In addition, a few of the spines on the top of the burr fish have accumulated white spots, and a few spines on its chin are drooping.
When we try to feed it, it is very interested, and attacks the shrimp, but is VERY easily scared away by the other, much smaller fish.