you all must av heard of the old saying feed a cold and starve a fever...the fast way to rid ybs is to reboot the pigeons digestive system...48 hours starve with electrolites oin water or beter still bicarb of soda..the stuff we use when ill with bad guts.....provided the droppings are ok..if slimy then they have picked up a secondary infection..probably ecoli, so an antibiotic maybe needed then...if you catch it early in the lethargic flying stage and crop retentrion the bicarb will suffice....once 48 hours up start with a light diet coated in natural yoguart from local supermarket....and build them back up slowly....they should be flyiong with vigour in a week...|Although siome appear ok and full of beans it would be wise to fas t them all..as it wont hurt...it will rid their systems of any impurities. please keep your birds loft bound during their fasting and rebuild till everything is back to normal....this is the practice i have followed for last 10 years and it has worked everytime