I feel like you have a very very crowded tank. Mandarins, aside from the pod population requirements, need alot of room to swim around and to hunt. The generally recommended tank size per mandarin is 100 gal
. Being that you have 2 mandarins, and 7 other fish, in a 55 gallon aquarium, I think that one of your mandarins is not going to make it.....and it looks to be the blue. You might try to find a new home for him before its too late.
How much LR
do you keep in there, if I may ask? They need alot of LR
. I am really, really concerned about the # of fish and size of your tank for those Mandarins.