A Swarm of Rhyothemis Species

I saw a swarm of Rhyothemis species at the top of forest tree canopy. I am not sure if the Rhyothemis was R. atterima, R. obsolescens or R. pygmaea (fulgens) as it was too far for me to make good judgement. The broad wings of the dragonflies looked black in colour from far. These three Rhyothemis species were present at the forest area.