In a cornie you'll need to drop it clear more in the FV and not bring as much yeast over, you'll always have 2-3 pints cloudy as the pick up for the cornie kegs is at the bottom so anything that settles out will be first to get in the pint glass.
I will transfer into secondary and leave to clear again before kegging in a cornie, I also filter some pales that go into cornies to make sure they are sparkling bright.
TG you'll need to check on your ratio's of Irish moss to wort, Is your boil a hard boil for the last 15 mins or is it a slow boil because you just dropped a ice cold cooler in to sterilise? Which yeasts are you using some are not as good as other clearing?