It's mostly a correction but consider that there are lots of people that are involved in ethereum mining based on the hardware market where there are lots of requests buying the motherboards, GPUs, PSUs. If you want to sell then I would advice to hold but if you need to buy then it's not a bad moment to buy as the price has been dropped a lot.
You are right, this may be a correction, but there is also speculation elsewhere that coinbase has been hacked.I dont think it is true, but there is some dumping of eth right now prompted by this rumour.
From coinbase; Investigating - We're investigating an issue with Ethereum sends and receives on the Coinbase platform. All Ethereum transactions will be delayed in the meantime. We appreciate your patience while we work towards a resolution.
Jun 20, 16:08 PDT
Other reasons could be the current congested network and outages because of extensive traffic.