You know how at the moment you have the data for trackers which are in chart or graph form on the left hand side of the chart/graph? Could you put the information on the right hand side as well? The stretch between is long enough that by the time you're looking at information on the right side, it's difficult to see which numbers it relates to. I have visual problems and thus find this particularly difficult, especially with the sleep tracker, but I think it'd be difficult for anyone.
Incidentally, it's great that you have different colours available for the backgrounds, both as a memory aid and for those of us with visual problems (e.g. dyslexia, Meares-Irlen Syndrome, autism spectrum and so on). It'd be great if you could add one or two more, perhaps one in apricot for instance. People with visual processing disorders often find that it is much easier for them to read with a certain colour as a background, but impossible with other colours, so the wider the range, the better.