Concern for my ex

Hey so for context me and my now ex are both 20 and were together for two years ( at uni together). We broke up on mutual terms because he was struggling a lot with stress and his mental health due to uni and home issues. I was upset obviously I mean it felt like the person I loved didn’t want me to be there for them. But the issue isn’t our relationship it’s what’s happened after. A week has past and he’s fallen into drinking and drugs to cope with what he’s going through but also doesn’t seem to see the issue with it due to his only friend enabling it. So the only person who would be like look u need to slow down a bit or are u ok would be me but is that my place anymore I mean he broke up with me so I wouldn’t be in this situation where hes doing this to himself. I just feel stuck at what to do. I’m seeing him on Saturday to sort the rest of our stuff out but I don’t know if I should say something or leave him to the life he’s chosen. For context when he moved to uni and made friends he did fall into weed and alcohol to cope then and only stopped when he fell out with those friends ( he doesn’t seek the drugs unless they are there but his housemate and only friend has been a constant smoker for two years). During that time he fell out with his friends he met me and never rly did drugs since we obvs drank but never to cope or anything. And he smoked weed occasionally maybe 5 times in the whole two years. I just don’t want to end things and something happen to him I could’ve prevented or been there to help him through. Any thoughts are appreciated.