It's probably the pullback to the breakout level around 5000.
It's all about support and resistance! Once we broke the resistance of 4950-5000 and climbed to new ATH it's always a question of time because the old resistance gets tested to see if it's build a new bottom, support level.
Be glad this is happening now. Remember the last big drop down to 3000?? The crash was so big because we hadn't tested this level! And when markets start to panic sometimes it continues to drop even further. Good that it didn't happen last time, but still it was pretty big drop.
So right now this is normal market behaviour and I wouldn't be worried too much.
We will test the 4950-5200 area imo, oscillators get a reset and then we may continue moving up again.
What I have left out here are the coming forks of course.