I started a new playthrough of Fire Red and chose Bulbasaur. Straight away I started to have problems. My rivals Charmander was able to 2HKO me with scratch. My Bulbasaur had trouble with some other Pokemon aswell. It was OHKOed by Misty's starmie using water pulse. My bulbasaur was 4 levels higher. Is there something wrong with my bulbasaur?
1) your bulbasaur has -s.def nature to be ohkoed by misty's starmie or maybe starmie's high s.atk got a high role that time and along with that you probably didn't get any special def EVs.
2) every bulbsaur has 49 base defence. In this case you might have got -def nature or blue's charmander got high role in those turns.
3) maybe you didn't notice they might be crits
Final view - either defences of yours might have -nature. You might also be unlucky and your opponents got highest role possible.
Hope I helped!