Explains everything.
It’s probably because of the team you’re using. Make changes to it, EV train them, ect.
Think about the Pokemon you’re using carefully and it’s not just about type advantages and disadvantages. It’s how they work with each other. A team is just a group if they don’t work to achieve a goal.
There’s a limitless choice with Pokemon team combinations. When you are choosing your Pokemon, you’d want to keep track on the stat builds, type, and moves. Try balancing out their strengths and weaknesses.
After testing the team in a battle simulator, you want to study up on stat values; Natures, effort points(EVs), and individual values(IVs), will make a significant difference if done right.
Hmm… You could always have a same type field move team. Like a Sandstorm or Hail…