I am by no means sure as your pics are very small, but the first thing that comes to mind is clubroot. Swollen roots, which are not hollow when cut through, are a good indicator.

It is inadvisable to leave brassicas remains in the ground - it gives the clubroot spores something to latch on to. Do not compost any of the roots, burn them or put them in the bin or you will spread it.

Unfortunately if it is club root you are stuck with it for the time being.

Can you try and post a larger picture - hopefully I am wrong in my diagnosis!