Chronic Respiratory Disease?

[Tweetypie]

Sorry to write again, but just wanted some more advice please.
Barbie "ex batt" has had a runny nose and sneezing for 10 days. It seemed to be clearing up, but today I noticed the clear (and bubbled) discharge is coming from both nasal passages. She is still perky, eating normal, alert and laying every day. The others are all well and no signs of similar.

Barbie sleeps on the floor of the coop (upstairs, not on the perch) and always has.
4 weeks ago I changed her bedding from dust free sawdust to aubiose. No other changes have been made. The coop is cleaned every single day and the doors left open to "air".

All hens have been wormed with flubenvet.

Considering her symptoms are worse today, as the discharge is now from both nostrils, any idea what it might be? She seems Ok, but I don't like to see her like this and wondered if she was in need of antiobiotics, which I am reluctant to give her unless absolutely necessary, plus it means a visit to a poultry vet. $$$

Just a thought, but do you think I should put a low perch where she normally sleeps in the corner, to discourage her from sitting on the floor? My thoughts are that any wee and poo she does during the night, might be giving off ammonia, despite being cleaned and new aubiose put down there daily. The floor part she sleep on is metal, as it slides out to clean, so cannot be soaked with urine, but the side of the coop is wood, so some might get in there. That's the only think I can think of.

Barbie is my favourite bird, I know I shouldn't say that, but I really don't like to think she is unwell.