Köi-Lö wrote:

Since the bettas are kept separate from the other fish at WW you have a good
chance of getting reasonably healthy ones. If any are in the tanks with the
other fish, you may not be lucky at all.
--

What you may not realize is that many will fill upt he cups with tank
water.
They add water to the cups when they come in, or instead of actually
cleaning them properly, they dump it out, and refill it with water from
any one of the tanks they choose.