In order for the graphs to be really meaningful and to draw conclusions there nust be at least three seperate measurements for each data point. This means 3 trials for each developer noted on a graph. Then the various points can be shown with error bars. It is only after this that one can be confident of the relative placement among the curves. It is possible that the curves for Xtol and your developer to fall within each others confidence limits.
The following site may be helpful http://www.pafaculty.net/biology/kei...Deviation.html. It's a lot of work but necessary.