I am almost done with current year's returns. But now I'm amending last year's; adding a couple of K-1's. Do I just update the same K-1's in this year's return?

You do need to update the K-1 entries in the current year. 

When you enter the K-1 form information for this year, you will see a screen that says Describe the Partnership, on which you need to check the box that says I have passive activity losses carried over from last year. On the next screen, you will be prompted to enter your carryover losses from the previous year. 

Technically, you need to amend the previous year tax return, since the original loss should have been reported on it. As a practical matter, it may not be crucial since the loss does not affect that year's tax, however.