They tend to like poor soil so maybe the soil is too rich or you are feeding them? I had a similar problem and the advice on here was to move them to poorer soil and since then they have done much better.

Also make sure they are getting enough sun--they need at least 4 hours of direct sun a day.

thanks for the advice ! I have been feeding them weekly since February with Richard Jacksons Flower Power from QVC (you're supposed to get more flowers using this) I didn't know carnations like a poor soil. So I will change tactics and stop feeding them. Hope I haven't lost the chance of flowers for this year .........

If they are in containers, you could try to run a lot of water through the soil--a once only thing--to leach out some of the excess nutrients. There should still be plenty of time for flowers this year, anyway. They usually don't make much stem growth until they are almost ready to make buds. Part of the problem with overfeeding is more blind stems (without flowers) and longer stems, which are harder to support.