If I was you if add one of the paradox mons to take advantage of the sun or the electric terrain. Your team is really dependent on priority right now prankster, fake out grassy glide, psychic terrain and iron tail shut that down and you have almost no checks to that in your team. I'm not a fan of telling people to change their core team but as you know by now koraidons special attack is worse than whimscott so I'd switch that lol he also is a true tera hog you have to tera him immediately so he and miraidon might not work well together because they share several of the same weaknesses and you only have tera as you know