Helmet head? Usually I help them along by hand as long as they are not dried out because if they are you may end pulling it off and killing the plant. Usually this happens if the seed is planted too shallow or if it was planted and heavy water poured and it caused the seed to float up shallow.

Agreed. But a month or two from now, it is unlikely you will be able to notice a difference between the plants any longer. Just glad they all survived and are doing well now.

Keep the RH up, they will come off

Wow, that is a huge "helmet head" problem there. But, I agree with Willard. Keeping them under a dome will keep the seed casings soft and pliable and allow the seedlings to expel them easier than if they dry out.