Finding minimum in the middle of a histogram
To me, this looks like you want something like 


start from right. Add up bins' values, as long as 


the added bin is larger than the last or
the value added by that bin divided by the current sum is still above a fixed threshold



Adjust the threshold to fit your needs.

Often, things like smoothing the histogram (effectively: applying a low pass filter to it) help. Or you do something like finding a function fit, something like a polynomial of fixed degree (let's say 5) that minimizes some error function (for example, sum square absolute error in all bins), and then analytically find local extrema.