Sick figure 8 Puffer?

ok well i have had my figure 8 for about a month now and all has been great. He's in a 29 gallon tank with 4 bumblebee gobs. plenty of hiding and swimming places and the salinity is arou 1.008 and 1.010. Have up to this point had no issues with anyone in the tank. My figure 8 eats like a cow every time i feed and is always at the glass when i walk into the room and is always following me throughout the room.

Well recently this last week or so he has been hiding a lot only coming out to eat and only when i spread it into the corner he now hides in. He seems to have lost some of his coloration and looks like a sleeping fish would { kinda grayish } all of the time. Any time i come near the tank or near where he is hiding he flips out darting form one side to the other hitting the glass or sand until he tucks back into a corner. Now i haven't seen any type of growth on him and his belly is still white and he still is eating. My question is what could be wrong with this little guy? Im new to the forum and brackish. i have kept my saltwater reef for around 3 1/2 years and also have a red claw crab brackish beach tank i just set up. any information would be greatly appreciated in helping me help my little guy out.

Anyone???