Root problem

1st post here I've just harvested today and when I took the plant out of the pot ther wer no roots on the outside of the plant with the result that the whole plant has yellow leaves with a poor harvest weight,I'm using bio all mix in 10 l pots an bio nutrients ph of 6.2-6.5 but being careful not to over feed also have intake and out fans with oscillating fan with indoor heater on all the time to keep temps up any idea what to try next to avoid this problem,many thanks in advance.

im no expert but you might have potted up too quik just a random guese i have had a realy slow growth/root problem recently and was told this was the problem i looked into repooting and pot size and problem solved

thanks for that just cant understand why leaves would yellow so badly