Hello there,
I am sorry that you and your friends are going through difficult time right now and thank you so much for reaching out to us. It is totally normal to feel confused and don't know what to do in this situation. When somebody we care so much are going through mental issues, we can feel how they struggle and sincerely want to do something to alleviate their pains. It would be hard for you at this point to confront them directly to address their mental issues but rather you could start from small converstation, as Golfing girl suggests, or share with them first how you have been feeling recently then ask them later how they have been feeling. You could always encourage them to actively seek help when they express hardship or difficulty.
Another important thing is your own feelings and mental health. It is really understandable to be influenced by the emotion turbulance of your cared ones. Yet you being calm, acceptive, open, and supportive along is the greatest help to your friends. I have felt the same pain and depression when my best friend was experiencing serious depressive episode, yet I eventually managed to collect myself together so that I could be a positive influence to support her recovery.
Please try to avoid being overly stressed or worried. Let time do the healing and everything will be okay.
Here are a few websites and resources that might be helpful in your situation.
1. For friends and Family members who experience mental health problems;
https://www.mentalhealth.gov/talk/fr...family-members
2. How to help a friend
https://www.nami.org/Your-Journey/Te...-Help-a-Friend
3. friendship and mental health
https://www.mentalhealth.org.uk/a-to...-mental-health
I sincerely wish the best for you and your friends.