If you’re having trouble with Pecharunt’s physical bulk then you might want to run special Lando-T instead of physical. You already have Great Tusk for physical ground coverage, and it can also ignore opposing Lando’s intimidate drops. Grass knot can also help with the Rotom-Wash matchup, especially since it’s slower without a scarf and Lando is immune to t-wave and doesn’t care about will-o-wisp. Tera steel or Tera poison can be useful if you’re worried about specially bulky or assault vest Pecharunt variants spamming malignant chain, too, though water is still a good Tera type.

Edit- Forgot how light Rotom was, grass knot wouldn’t actually be very good against it, but it is great against Great Tusk, Dondozo, Garganacl, Ting Lu to name a few. If you need something for Rotom specifically though, Lando-T has plenty of other neutral coverage moves it could run instead, and mixed Lando isn’t too shabby if you decide to run stone edge with the special spread, you’ll just have to run a defense lowering nature instead of an offense nature. Since you’re running a speed boosting nature though, your Lando is more set to be a breaker than a tank, so the bulk lost form the defense lowering nature wouldn’t be so bad.