@WAMcCormick
Most probably the soil is too compacted to allow the root to get a hold - and/or there isn`t enough weight of soil covering to give a little top resistance.
Are you using seedling mix or coir etc?
I have had this on occasion and with these few seeds I just lifted them and used a small needle to make a hole for the root and then re-postioned them adding a little covering of media.
When/if you use the sand method they need just 1/8" of sand as covering.
When planted it is quite important to only keep them moist as too much water can stunt their growth, and even rot them.
