Soft Egg Shell

I've had those before - funky aren't they? Anyway, are you feeding them oyster shell? You should offer oyster shell in a separate dish so they can take what they need, year round. Occasionally a hen will have a temporary glitch in the egg laying machinery, so you may not get any more. However, it can lead to infection if one breaks inside her.
You said you were feeding one scoop of feed for 9 hens + left overs? They need more chicken ration. Each hen eats about 1/4lb feed/day, more in the winter. If you feed free choice they can eat what they need.
The egg? you can eat it...

 

If this is an isolated incident, don't worry about it as long as you're feeding enough calcium. If your hens aren't getting layer feed or oyster shell on the side, that very well could be the problem. Also, if you're feeding dry feed, it's best to feed it free choice so the hens get all the calories they need. It requires a lot of energy to build a proper egg. If you're under-feeding your hens, they will come up short nutritionally.

If this hen continues to lay soft shelled eggs in spite of being offered plenty to eat and adequate calcium, she may have a problem assimilating calcium, although this is not as common in such a young layer. I've had very good luck getting older hens who lay nothing but "rubber" eggs to start producing hard shelled eggs by administering calcium citrate at a half a tablet per day or as much as half a tablet twice a day until the eggs appear normal again.