Maybe it still A bit stressed
I only got it yesterday, the colour even a bit daarker when i pick it
The water wasn't great in that LFS
I will try my best to save it
About the interest thing... I'm not really sure what to tell you. I've had flowerhorns in the past who weren't especially active and I've had flowerhorns who were extremely active.
Well that seems like that would be the problem... If you just got him, he's probably stressed. If he doesn't seem to be improving within a week to two weeks, a new approach might be necessary