CLIPPER was an appropriate treatment, especially if the pond is prone to significant flow-through events.
Not sure if the CUTRINE was necessary; I suppose it's possible, assuming algae was present or anticipated.
CLIPPER will generally do a fantastic job on both duckweed, watermeal and several other species - but, has a very limited duration of herbicidal activity. Then again, not even fluridone (SONAR, etc) could provide residual activity in a pond with transient water-flows.
Assuming the CLIPPER treatment remained isolated in the pond for 24-48 hrs following the treatment, I would expect excellent results on the "existing populations" of duckweed and watermeal. However, weed-rebound from germinating seeds (unaffected by the treatment) should be anticipated in the future.
I'm guessing the transient-flow of water during the recent rain-event was insufficient to "flush" much of the duckweed and watermeal down the creek. Yes?
