WHen I saw signs of coccidiosis I put them on antibiotics and corid for 10 days then followed up a couple weeks later with another 7 days of corid.
What type of antibiotic are you using?
Just so I understand correctly I'm a little confused by your post- you have given the Corid 2X and are now on your 3X giving it?
Tell us more about what you're feeding - any other foods and are you adding any type of supplements to their water besides the Corid (in the US medicated feed has a Coccidiostat in it - though it's a small amount - this is just a preventative dose at best - usually Amprol/Amprolium (Corid) is what is used).
Tell us more about the symptoms you are seeing - I'm just trying to understand more about what's going on - photos may be helpful as well.