Villagers not doing jobs

In my man-made village two farmers would farm using my farms I made. They soon stopped farming  after I threw them stacks of bread so they'd reproduce. Since then I've thrown carrots into their inventories and they picked it up so their inventories are not full. Also it is difficult to find jobs for the villagers as there is a large delay between placing a block which has a job associated with it, and the villagers becoming that job.