Edit. The change of decor and environment could also add to his mood problem.
Maybe what he/she needs is a place of refuge in the aquarium.
So it might be beneficial if you moved the rocks and driftwood around so that there is a little cave to feel comfortable in.
I'm not sure if that fits the mala's behavior but it seems to work for most of my fish.
And also the previously stated factors such as the dithers,, floating plants, etc.