Interesting I would have guessed at Electus on that guy. I honestly can't comment on color as my JB totally morphed to green from the original orange JB color in my system. Yours kinda looks like its doing the same. Maybe it is lighting.
What kind of par are they sitting under?
Where's your No3 and Po4 at?
There's gotta be something to it and probably a correlation of these things.
I can say mine is just keeping the color and getting more vibrant as it goes.
Super hardy as well been with me from the beginning