It commonly called 'weak snick'. Best bet for you is to post to the disease forums of seahorse.org or syngnathid.org. Post the age of the horses / or how long you've had them, whether they are CB or WC, what species, the size and filtration used on your tank and what you feed. All the water quality values you can think of will also help.
Best of luck. I really cannot remember if this tends to become something more serious. You can also try searching the disease forums of both those above websites with the phrase 'weak snick' to see what you can turn up.
>Sarah