Hi, welcome to the forum.
It is not really clear what you mean by a common y-axis. I think we need to see more of your your code and some sample data. If possible can you point us to an example?
A minimal reproducible example consists of the following items:
A minimal dataset, necessary to reproduce the issue
The minimal runnable code necessary to reproduce the issue, which can be run
on the given dataset, and including the necessary information on the used packages.
Let's quickly go over each one of these with examples: