Did you not transplant the whole rootball? Maybe it wasn't root bound yet.I transplanted my strawberry haze, from mg soil to fox farm, when i took the plant out, i noticed a bunch of roots left behind in the soil, is this normal when transplanting, for some roots to get left behind, and the plant just grows more roots.
I think transplanting was the right thing for you to do in this situation. i probably would have just watered with straight ph'd water though with no nutes.i had miracle gro soil with slow release nutes, mixed with sand and peat, i transplanted to fox farm ocean forest / verm/ perlite and i did get the root ball. I transplanted then watered with a solution for every watering of Fox farm grow big.
I switched because i was getting nute burn, from the mg, so i asked and someone said i should transplant.