I like your "time lapse" feel with this. Something about it isn't connecting, it's feels cold and disconnected in some way. Perhaps it's the precise lineup? Maybe the studio feel? Possibly the lighting? Not trying to be rude, just kind of thinking out loud. Sorry I can't be more specific for you. Good luck in the challenge.
Kind of a stretch to make the picture meet the challenge, but OK. The apparent color change seems to contradict the idea of a single crayon being used up (over time).