This looks very similar to a problem I'm currently having in my geometric network (sewer).
The problem could be disconnected or disabled features. To find these you will need to see zoom in at each location (very close) to see if there are any gaps between edge and junction (can be very hard to spot), and check the attributes of the first untraced edge and the junction to ensure the Enabled flag hasn't been set to
Another option is you may need to rebuild connectivity for your area of interest. The third button from left on Geometric Network Editing toolbar is Rebuild Connectivity
Activate that tool and draw a small box around the area the trace stops then trace again. You may need to re-establish flow direction after each time you run this tool.
If that improves the trace, then draw a larger rebuild extent with the tool.
Note that if you rebuild a very large area with a lot of features it can take a very long time to run.
You can see that even after I have completed my Rebuild Connectivity there are some connections that are still not tracing. These are a combination of two reasons - one the flow direction is wrong (my geometric network uses digitised direction as flow direction), the other is the gaps I mentioned earlier. Many of these connections are not quite snapped to the main edges, and so the trace doesn't reach them. These need to be manually snapped (trim/extend) and then use the Rebuild Connectivity and re-establish flow direction. Once this is done everything traces fine.
If you have a large network this can take some time to solve, however once it is done it shouldn't need to be redone.