This depends on whether or not the clubroot was already in the soil, or whether you have unwittingly imported it on the plants. If the plants were raised from seed in that soil, then clearly the fungus is already there, and you might as well let them continue - how they fare will to some extent give a clue as to how bad the infection is.
However, if you brought the plants in from outside, or raised the seedlings in a soilless compost (particularly one containing peat), then there is always the possibility that you imported the infection with the seedlings. Check with your neighbours to see whether they know of any previous clubroot on your plot or any adjoining plots. If they do not it might be well worth your while to remove the plants, together with all the soil which has been in contact with the roots, and then sterilise both the bed and your tools with Armillatox. That way you stand a fair chance of nipping the infection in the bud.
Liming should be carried out in the autumn.