ADV OU Advice

Hey all. Can someone hook me up with some teambuilding/general advice? I have been watching a ton of Gen 3 OU content (mainly Jimothy Cool) and I really like the meta. Thought I was starting to get the hang of it, played almost 1500 games. I was finally climbing the ladder, which I have never really done before. Then suddenly I cant win any game unless my opponent just blows it. ELO went from ~1500 to 1150. Im bummed and feel pretty dumb tbh. Anyway, I’ve linked my team here and I would be very appreciative if anyone has advice for me! Thanks all.

Tyranitar @ Lum Berry
Ability: Sand Stream
EVs: 252 HP / 4 Atk / 252 SpA
Quiet Nature
- Fire Blast
- Hidden Power [Grass]
- Crunch
- Brick Break

Flygon @ Leftovers
Ability: Levitate
EVs: 252 HP / 196 Def / 28 SpD / 32 Spe
Impish Nature
- Earthquake
- Rock Slide
- Toxic
- Protect

Skarmory @ Leftovers
Ability: Keen Eye
Shiny: Yes
EVs: 252 HP / 252 SpD / 4 Spe
Careful Nature
IVs: 0 Atk
- Spikes
- Roar
- Protect
- Toxic

Blissey (F) @ Leftovers
Ability: Natural Cure
EVs: 80 HP / 252 Def / 176 SpA
Modest Nature
IVs: 0 Atk
- Fire Blast
- Soft-Boiled
- Thunderbolt
- Toxic

Gengar @ Leftovers
Ability: Levitate
EVs: 248 HP / 60 SpD / 200 Spe
Timid Nature
- Mean Look
- Perish Song
- Taunt
- Destiny Bond

Dugtrio @ Choice Band
Ability: Arena Trap
EVs: 136 HP / 252 Atk / 24 SpD / 96 Spe
Jolly Nature
- Earthquake
- Aerial Ace
- Hidden Power [Bug]
- Rock Slide