Listless Adult Platys With Clear Poo

[Mamashack]

Hi there am brand new to this site - have posted on an existing thread but the last post was November '12 so am starting a new one!
Have 2 adult platys 1 male 1 female. Had them 6 months - they were about 3/4 grown when I got them. Started producing fry last month, got 1 fry about 5 weeks old and 5 young fry only 1 week old today. The little ones seem ok but suddenly yesterday mum and dad became very listless, they're not eating, and worryingly not interested in chasing the new fry like they were or at least mum was!

Have an Aqua One tank 27L altho probably less with plants and filter and gravel - maybe 23-4L
Fluval U1 filter
Interpet Delta therm heater 25w - which has only been in a couple of days - tank light seemed able to keep temp between 23-23 degrees until the recent cold weather.
Put new plant in there about a week to give the young fry somewhere to hide, also started feeding them with Liquifry no.2 on Friday (2 days ago)

Tanks stats
ammonia - 0,
NO2 - 0,
NO3 - 0-10,
pH - 6.8
chlorine - 0
GD - 16
KD - 3

The adults have clear poo since yesterday and are refusing to eat. Could it be parasite? There's nothing to see - no white spot and no worms hanging from the anus. It started so suddenly - it was like someone had flicked a switch!
Tried 10 drops Myxazin this morning in case it's bacterial - half dose because of fry. It was all I had to hand.
Haven't a clue what's causing it - does anyone have any ideas? Please?

 

[Mamashack]

Update:
Fully expected to see 2 dying if not dead adult platys this morning, but they were swimming around like nothing had been wrong yesterday! Put some fry food in and they devoured it - don't think the fry got a look in! Will continue with Myxazin just in case that's what helped. Should I double the time to 10 days since it's half strength or stick to 5 days?

 

[PrairieSunflower]

Glad to hear they improved, sorry to see no one posted any help.

Sometimes clear poop can be normal, such as when they don't eat for awhile. Its the combination of listlessness that makes it more worrying. Glad to hear the meds seem to be helping.

 

[Mamashack]

Thanks Prairie - do you think I should stick to the 5 days course or double it because I'm giving half the dose as recommended when fry present?
I've also been splitting the dose further as the fry seemed to get a bit antsy with even half dose so I'm thinking of giving quarter full dose in morning and same in evening. Will that be ok do you think?