Completely stuck on Tate & Liza in Pokémon Emerald (Poison Monotype) – Need tactics!

Hey everyone, I've hit a massive wall against Tate & Liza and could really use some advice. I'm doing a Poison monotype run, and facing Psychic-type gym leaders with a type disadvantage is brutal. (Just to clarify: I traded in all these Pokémon from other generations to make this team possible!)

My available team options: Muk, Qwilfish, Ariados, Nidoking, Nidoqueen, Crobat, Gengar, Tentacruel, Weezing, Arbok, Venusaur, and Dustox (I can bring 6).

Their team: Claydol, Xatu, Lunatone, and Solrock (that Sunny Day + Flamethrower combo is tearing me apart).

The level cap is around 42, and even my level 44 Pokémon are getting destroyed. Does anyone have specific strategies, movesets, or team combinations using available Poison types to break through this deadlock?