I have posted about my friend before and need some advice. I am unsure of when to try and talk to them about some questions.

They are coming out of a bad battle with depression and returning to theirself. I have seen them to check in and have regular communication to. I need to talk to them about some of what happened and some things they said in the beginning of the battle. How can you know when it is ok to do that? I need to know some things but do not want to cause them to fall back into the battle. Thank you for the help.