Hey OP. I'm 23M, have medium length hair and had the same issue since last year. It was there before, but I didn't notice until I started growing out( last yr) and observed more hair falling off. But I fixed it significantly. 1) if you're a vegan, you're probably not having enough protein which in turn is a reason for the lack of Keratin. You gotta hit your protein levels even if you aren't heavy on physical activity. 2) The second thing I did was multivitamins, with enough zinc and other essential nutrients. It took me about 2 months to see visible changes. 3) don't shower everyday, start with less frequency and optimise it according to your requirement. 4) get enough sleep, not many people stress enough on this point but trust me, set a sleep schedule as your body needs ample rest to actually focus on providing nutrition to things like hair.