ajohn

Bad weather at this time of year often results in flocks of egrets suddenly appearing in various locations. These are presumably migrants on their way north.
This is a behaviour I associate more often with Cattle Egrets (although is no doubt possible with Little Egret). You mention that there are apparently some Cattle Egrets in this flock - I don't know how close your views have been but is it possible that more are (non-breeding plumage) Cattle Egrets than you initially thought?

ajohn

Interesting record - these are presumably migrants (Hong Kong Little Egrets are breeding already!)

My previous post was really in case you didn't have clear views, which you clearly have. I hope you didn't interpret it as a suggestion you couldn't ID these species!