Your team has a major weakness to ground and fire types. The weakness of all your Pokemon when they are fully evolved are:
Chestnaught, Grass/Fighting, Weaknesses to: 4x to Flying, 2x to Poison, Fire, Psychic, Ice, and Fairy. It resists Ground, Rock, Water, Grass, Electric, and Dark.
Blastoise, Water, Weaknesses: 2x to Grass and Electric. Resists: Steel, Fire, Water, and Ice.
Pikachu/Raichu, Electric, Weaknesses:
2x Ground. Resists Flying, Steel, and Electric.
Pyroar, Fire/Normal, Weaknesses: 2x to Fighting, Ground, Rock, and Water. Resists Bug, Steel, Fire, Grass, Ice, Fairy, and Ghost types have no effect on it and vice versa.
Aegislash, Steel/Ghost, Weaknesses,
2x to Ground, Ghost, Fire, and Dark. Resists: Flying, Rock, Bug, Steel, Grass, Psychic, Ice, Dragon, Fairy, and can't be damaged by Normal, Fighting, and Poison types.
Based on typing, your team is strong against Ground, Rock, Water, Normal, Steel, Ice, Dark, Fire, Flying, Bug, Grass, Ghost, Psychic, and Fairy types.
I recommend getting a Fairy type like Sylveon for your team. It can cover Dragon and Fighting types. It doesn't have many weaknesses in Poison and Steel types, plus it has an immunity to Dragon types. I also suggest teaching your Pokemon TMs so they can cover their weaknesses.
Hope this helps.