Help Is something wrong?

I have a small flock of 7 birds from 20 to 30 weeks.  All the girls are Hybrids.  5 are laying very occasionaly.  We get 1 egg normal size egg from our Maran type the rest are like blackbird eggs in size.  And have not increased in the 7 weeks since the girlsstarted laying.  They are fed on layer pellets wormed regulary as they are on the same ground their run bye the way is 35 x 25 foot square.  Is it normal for the egg sizes to stay so small for so long?   Any advice would be appreciated.  The girls are as follows

1 goldline
1 sussex
1 speckaldy
2 black rock type
1 white leghorn
1 cream legbar hybrid

All were purchased from reputable suppliers and are full innoculated as follows
Day 1                Mareks                                 Hatchery Injection                Injection  

Day 3-5             Salmonella enteriditis          Gallivac Se                           Drinking water  

Day 17-19         Salmonella enteriditis          Gallivac Se                           Drinking water  
  
Day 25              Infectious Bursal Disease     Intervet - Gumboro D78      Drinking Water  
 
Week 8             Avian Rhinotracheitis           Merial Nemovac                   Spray

Week 10            "Inactivated ND/IB/
                           Egg Drop Syndrome"        Intervet IBMulti+ND+EDS    Injection    

Week 13          Avian Encephalomyelitis     Lohmann Avipro AE               Drinking Water    

Week 14 to      "Inactivated ND/IB/
transfer             Egg Drop Syndrome"          Intervet IBMulti+ND+EDS    Injection    

also a couple of weeks ago I thought I heard sneezing a couple of times but after watching closely could not see who it was or even see a sneaze.   Hope this helps.

Hi Michelle they are on Heygates layers pellets the leghorn is the youngest she has been seen visiting the nest box but nothing as yet the other are laying on and off but only 1 regular size egg.  Just wondering how long they lay the small eggs for the Maran's egg size has never changed since we got her she was the oldest her comb was just going red.

Hi Angus,
I have never heard of Heygates feeds before so I couldn't say, I use Marriages, like Grumpydad said usually they only lay small eggs for a short while 
Could it be that all of the hens have started to lay? as when they first start they are not very regular.
Sorry I can't be of anymore help I don't have any experience with hybrids, but this is a strange time of year for chickens, with the days getting shorter.
But I do have White Leghorns so when she starts to lay you should get eggs from her over the winter.
Michelle xx

Perhaps you could post some pictures of your chickens and eggs, we might be able to work out whats going on 
Michelle xx

yes the eggs are normal in every way but small except the eggs from the Maran type which are normal size.  I just thought with what I had read that the size increased quite quickly.  You know what its like though with the kids our demand at the moment far exceed the supply.  Everyone wants an egg for their breakfast, that is why also we tried to get birds which hopefully will lay slightly different colour eggs.