1 year old hen stopped laying for no reason

[SkyAJK]

I have a mix breed hen from a Isa Brown rooster X Silverlaced Wyandotte hen.

She started laying egg around 6 months old. 6 to 7 eggs a week for around 4 months and suddenly stopped.
She would sit in the nest box for a few hours every day, but not laying any egg.
She has been sitting in the nest box for a few hours each day for around 3/4 months now.
We are in Summer in Australia here, so she should be busy laying egg or going broody, but she is not doing any of it.
She is not molting
I did the usual check for lice/mites/worm - treated for worms.
She is eating and drink well
She has a bit of weight on her.
She is at the bottom of the pecking order so get peck at
There is a lot of space in the run for 5 hens in it.

I read a some posts of same on here, but I have not find any answer for my hen.

I am thinking perhaps I could just give her some antibiotic, it might help if she has some sort of issue.
Chicken is good at hiding illness, I don't know what her illness might be as by appearance she is looking healthy.

Could anyone please advice on what my hen might be having, and what can I do for her? Thanks.

 

[Rand0]

might be stress since that is something that made a hen of mine stop laying eggs for a while.anything loud or any pets like dogs?

 

[SkyAJK]

She was hatched under mother hen & she grew up with them barking and hanging around the garden. She might be used to this already?

I am not sure if there is anything I can do to ease on the dog barking. I have 1 dog that give me headache when he barks because of the loudness of his voice. I can not fix this barking issue though.

 

[Rand0]

She was hatched under mother hen & she grew up with them barking and hanging around the garden. She might be used to this already?

I am not sure if there is anything I can do to ease on the dog barking. I have 1 dog that give me headache when he barks because of the loudness of his voice. I can not fix this barking issue though.

oh that might not be an issue and I'm not sure loud sounds are causing stress for her. have you added any new hens in the coop?

 

[SkyAJK]

No new hen before or after she stopped laying egg.
Edit to add more info:
Her face and comb are bright red, and her pin bones are 3 fingers width. From my understanding those are signs that she is laying.
Her stomach some days is a bit full, but soft. Most of the time it is normal that is slim like my other hens that are laying.

 

[Rand0]

No new hen before or after she stopped laying egg.

have you been cleaning their coop? or have you been? a dirty coop can cause chickens to stop laying eggs.also what have you been feeding her?

 

[BigBlueHen53]

Are other hens still laying?

 

[SkyAJK]

Yes, the coop gets clean every morning and new bedding put in before bed time.
I use card boards as bedding material and remove each morning. I pick up their poops a few times a day.

Yes, other hens are laying, not every day. My Isa brown lays egg every day, and the heritage breed a few eggs a week.

 

[FrostRanger]

Might she have a secret nest somewhere? I'd check anywhere she hangs out at very carefully just in case. It is also possible she's just taking a break. Hens do that sometimes. Nothing you can do about that except wait

 

[StinkyAcres]

Any possibility of a hidden nest somewhere?

EDIT: @FrostRanger beat me!