If your coop is dark that would make them stop laying. I have lights set on a time to give my chickens 14-16 hours of light a day.
locking them in side might have something to do with it to when it is cold and I lock my chickens up there laying decreases.
You could put her in a dark room with no light it will make her not want to lay and the problem might fix itself if you try this let her stay in the dark room for a couple days and the check her for blood. If she still has wet blood on her I would call it.
It is normal for the to lay soft eggs or lay 1 egg and the another egg a couple days later but is this happens when she is a month or 2 later
I would feed her oyster.
If this is the first time you found blood on and egg she is probably fine. It happens to my eggs from time to time.
Hold the fertilized eggs under a REAL bright light and you should be able to see if the chick inside is forming. If you can not see a chick the light my not be bright enough if...