Yes, this is common. Yes, you should wait for the K-1's to do the taxes. If you file without the K-1's, you will be required to amend the returns when you receive them.
If the K-1's have not been issued and you are nearing the deadline of April 15, 2020, I recommend filing an extension. To file an extension see this article for instructions: How do I file an extension?
Any tax owed will still need to be paid by April 15, 2020.
