Hard to say Lorraine without knowing more. Sorry about it, all that effort fturning into stems is not good.
Possibly you were a little early sowing the fennel (before late June?) or it was too dry for a while as it loves moisture and dry roots can trigger bolting. Has anyone ewlse had success with fennel from June sowings?
Celeriac, if you sowed it after mid March with gentle warmth for the first few weeks, and have kept it moist, should not be bolting. What variety are you growing? Is anyone else having this problem with celeriac?