Ah soil is killing me, i replanted them 2 weeks ago. Do i need to get larger pots already? they are growing in 3 gals right now.

What is the best way to check for plants being root bound without disturbing the plant or hurting the roots much?

There is a hydro shop opening in my town today actually and they sell fox farm ocean mix. Would it be a good idea to switch and if so how do i get rid of the lower quality soil the plants are already in?

I am not sure how they got an exess of N. They only fertilizer I have been giving them has been every other watering with 1tsp per gal of water.