Nute locked is generally due to a build up of toxic salts. This is from feeding and not flushing the medium every few weeks, sometimes its required even more frequently. If you have nute lock you will see all sorts of def's or are just unable to fix it. Common mistake is feeding it more . Think you got nute lock? Flush your pots out with 3x the volume of the container. dont let it dry(dont feed) make sure its a good flush to remove all those toxic salts!