It's due to integer effects with low counts for the class membership.
Consider the "Not Filipino" graph at the lower left. Note how the lower left line goes through the point (-3,3). That point would correspond to 1 observation of a Not Filipino out of $10^3$ people in the neighborhood. Note also that for the Chinese graph, the line goes through the same (-3,3), and likewise for the Disabled graph. The lines also go through the (-4,4) point - one observation out of $10^4$ people. If you consider where one observation out of 3,500 people would lie (at (-3.54,3.54)), you can see how the line gets generated.
The next line to the right goes through points that appear to be about 0.3 x-units larger than the first line; this is the line corresponding to two observations of Not Filipinos, or Chinese, or Disabled (log10(2) = 0.3). Since you can't observe between 1 and 2 Not Filipinos, you have a gap between the two lines.
These things happen, I've seen similar myself.