at least you know your plant is really healthy i have seen worse and i think your plant will love the new pot i think the only reason all your roots went straight down was because of your mixture you had b4 was basically a hydro and the roots go down and you will have a nice thick stem also the only bad thing about this is you are going to have to water more often which is actually a good thing. in my first set up i would water once every two days so in a week i would get maybe 2 3 feedings you would get 3 or 4 in a week which is better feed one day water the next feed the next and so on... and dont forget to keep checking the weigh by lifting the pot to see the difference of wet and dry. you might want to invest in some,big bud ,sonic boost,jurassic bud, ton o bud,brix plus,sugar daddybasically something to help with a bit of mass and resin , would also reccomend getting away from mg fert for budding for now its ok as you can see with your roots. gud luck on your journey.