Yo ok i tell u in details example u catch a pikechu and its have in and ev how u know which one is in and ev when u open the pokemon bar u see a orange colour point like atk31 spd 25 sp atk 31 sp def 21 and hp 28 but after beside the iv u see a blue colour set which is empty cause u dont battlr him when battle with another poke the ev gained and there are aldo some berries who can reduce ur ev like u unfortunatle ev tran ur pike hp the u can use the berry maybe this will help
I tell u the thing is the player was used a rain team u know in rain team if weather is rain some pokes spd increase like ludicolo,omastar,kingdra,kabutops etc.or maybe use qwick claw it increase speed also