We need a few more details, Sjw. What kind of compost were they planted in? What were the temperatures like in the greenhouse? Once they came up, did you feed them any, and if so, what?

They are in compost especially for seeds and have not been fed. We have had warm weather and now it is cold and wet, they just seem to be very slow and not big enough to prick out and the surface of the compost and perlite is going green.

I would give them a mild liquid fertilizer, such as half-strength fish emulsion. For future crops, check to see if the seeds that you are planting need to be stratified--I believe that Delphinium seeds do--and take note of the temps in the greenhouse when you sow. Both Delphiniums and Penstemons sprout best at low temps, a little below 18º C.

mine stalled as they got too hot and I put them in a cold frame outside and they have started into growth now.