"we just followed the crowd of 19 faithfully” doesn't really make sense, as you are saying 'crowd of 19' - which means 19 people! "we just followed the crowd like other 19 did" is not grammatically correct. I think that if you wrote this, most readers would think you meant "we just followed the crowd like the other 19 did" - which means 19 people followed the crowd, and then you did. A key phrase for you is '19 year olds' - i.e people aged 19. Perhaps "We acted like other normal 19 year olds, and faithfully followed the crowd" or "We acted like other normal 19 year olds, and just followed the crowd" - since usually 19 year olds don't really do anything 'faithfully' ;^) or more simply "We just followed the crowd, like most normal 19 year olds"

We acted like other normal 19 year olds. We followed the crowd, like other 19 year olds. We followed the crowd, like all the other 19 year olds.