Sorry for the delayed response, I didn’t see this until now.
Now that they are in two different streams, are you able to use the SpatialRelator like I suggested previously? This will find the topological relationships between the two streams depending on what spatial predicates you are testing for. You may also want to use the TopologyBuilder if the first transformer does not yield the results you are looking for.
Send us your workspace so far, or screenshots, so that we can help further.