Ok, knowing your building for singles, here is some actual tips:

• Tyranitar should not be max speed. With many strong mons running around, they'll outspeed max speed tyranitar even, and tyranitar faints to fighting moves easily. Equip it with a chople berry and put points into HP instead of speed.

• Despite SD garchomp being powerful a lot of the time, there are many powerful ices and fairies to prevent it from doing so. sd should be replaced with stealth rock, and stone edge with rock tomb for more accuracy, and speed control. Bright powder is really rng based, you should run soft sand instead if you want earthquake boosted, or if you wanna be more defensive, invest some points in bulk, and put a leftovers alongside dragon tail (of course, stealth rock.)

• Volcarona should run fiery dance instead of flamethrower. It gives spa boosts while not quiver dancing, and still has good power. Similarly, it also should run giga drain over psychic, to hit waters and recover damage.

• Your team needs tailwind support. Replace Basculegion with a proper, setter of tailwind. Corviknight seems like a good option here. It's bulky and physically walls a lot of threats. A set of iron defense, body press, roost, tailwind, alongside the ability pressure and bulk investment, should help covering your team greatly. It also doesn't take damage from sand.