Hen poo problem

I have had my 4 hens for just over 3 weeks - 1 goldline and 3 RIRs.  I was told when I bought them that they were all laying or POL, although I'm only getting about 5 eggs a week in total.

I found what either looked like lice or a mite on the goldline and have twice scrubbed ou the hen house with Jeyes and Poultry disinfectant, and scatter Daitom into corners of house, nooks and crannies, and into their bedding.  I also rubbed the powder onto the hens, and followed this up a week later.

Yesterday and today I noticed that the goldline is passing what looks like water.  Referred back to the poo cheat sheet posted by Aunt Sally and it looked similar to the watery poo (although without the lumps in it).  The description on the page says that either the hen is too hot (which I doubt given our dreadful summer) or that it isn't eating enough.

The hens always have food and drink in their run - a mixture of Allen & Page layers' pellets, mixed corn, and mixed grit.  The food is in a container easily accessible under the hen house so is dry and clean.  They get fresh water every day.

On top of this I give them daily treats such as veg scraps, a little spaghetti, cooked rice.

Every time I go to the run, they come rushing over and gobble up anything I give them as if they're ravenous, but they just don't seem to be eating much of their pellets and corn.

Where am I going wrong? And what do you think this could be?

Should I try layers' mash?

I wouldn't worry too much for now this will probably go as suddenly as it arrived, I have had this a few times before and it always seems to have happened at a time of stress, such as new arrivals. Just keep an eye on them and avoid anything which may cause stress, lice wouldn't help the situation.

HairyBear have a look at this link for treatment of external parasites:-

http://chat.allotment-garden.org/index.php?topic=5250.0

My vet prescribed the Frontline spray to treat mine with (as a precaution) although most on here use the drops.
Joyfullxx