ShinyBlackInfinity

Pokemon rejuvenation question:

Hey, I need some help.

I have a problem, I'm trying to do the battle in chapter 15 vs Angie and Celia but I don't have pokemons at a good level that can change the weather to sun, what can I do?

My team is composed by:

Seismitoad

Silvally Dark-type (for this fight I changed my Delphox with Silvally)

Sylveon

Zoroark

Nidoqueen

Zebstrika

The pokemons that gives me more problem are walrein, beartic and Ursaring, mostly because I arrive at that point of the battle that I don't have my team alive, and Ursaring ice punch is too strong in combo with Beartic. Rotom and Mamoswine don't give me too much power, because I use Zoroark and Silvally in combo to defeat rotom and seismitoad use Drain punch and surf on Mamoswine, also Morpeko is not too difficult, because my sylveon one-shots it. Unfortunately i finished all my ultrapotions (I only have one) and I assume I can't find any heal item inside the manor. I also tried to beat Angie's pokemons before Celia's pokemons and the other way around (like someone suggested on reddit), but without a big success. I've been trying for 10 hours without any success and I don't know what to do anymore, I really need some advices for this fight. I play in casual mode but this fight it's becoming impossible (I'm ok to use cheats to beat them if that means continuing with the story). Thank you in advance for the advice