well the wet dropping can be a number of thing from safflower in the seeds been off to the stress of been out of the comfort zone of the loft or indeed ailling , they could be eating the smaller seeds and filling themselves with water so they feel full but as there now flying a little they may need a more nutrianal feed , beding on the floor with ybs helps them from not been in contact with there own droppings , it could well be something or nothing so get them tested perhaps mix a small amount of grit in there feed may help the cider vinegar is a good idea as will stablise there gut and be hostile to bacterrial infections naturaline is good for this as well and some vitamins wouldnt go a miss either.