Feeling responsible for my exbf (tw: drugs)

Problem/goal: exbf is doing drugs after the break up

Context: The past few weeks were chaotic, and we ended our relationship na. But I just learned that he is smoking weed now. I feel responsible for his decision to do drugs cause he has been so stressed about me daw. I don’t know what to do. Cause if hayaan ko lang siya despite knowing, it might do him harm. I know naman hindi sobrang sama ng effect ng marijuana but it is still illegal. I am concerned about his safety and wellbeing. Should I talk to him again and fix things? :(

Previous attempts: none so far.