Yeah defo stressed if losing colour.One clown fish seems to have taken a turn for the worst and colour has changed..
If late now .after work tommorrow try look at fish best you can and get some photos up so others can see your remaining fish as losing colour not good sign but im not expert.
I hope its just temp related and he lost colour as stressed.my tank sitting same as yours noe at 28 degrees and mine seem ok so far ( touch wood) as i know im only one step away from being up that creek without a paddle lol )