flubenvet and runny poo

Is it normal for chickens to have very runny poo during the one week worming process?

I've been using the 1% stuff and putting a 6g scoop into 2kg of food, then feeding my girls nothing else but this (although as I have six will have to make up another 'batch').

Started on Friday and poos are now very runny - not to mention chickens are sulking at lack of usual greens/corn/late afternoon 'treats'!   I've followed the instructions to the letter so am a bit concerned that this could be some other problem although the girls seem quite happy otherwise.

Incidentally, got a 60g tub for £12.50 inc p&p on animalmedecines dot com (or something like that) - is this reasonable?   - it certainly was an improvement on the £29.50 quoted by my vet!

hi, when i flubenvetted mine, it didnt seem to make that much difference to the poos.
That`s a great price by the way, i paid 16.00 for a tub that size.x