It looks like they could have diarrhea. This could be from a few different causes.
One could be stress, going through a sales barn has to be pretty scary.
Second could be a change in feed like more grain than they are used to, or more grass, etc.
A third would be Coccidia. If that's the case you would want to start treating them with Corrid sooner than later.
A fourth could be a disease called Johnes which is an incurable wasting disease in goats, though yours look like young goats so this probably isn't the case, but if they are over a year it may be worth testing if this doesn't clear up.
A fifth could be CAE, also an incurable disease in goats, and can cause them to to be un-thrifty and have soft poop.
And a final sixth option could be they have a heavy worm load. Worming would be a good idea not knowing where they came from in either case.
It wouldn't hurt to have a vet come check them over. I know buying goats from a sales barn is risky as many people send their sick ones there. This is not an exhaustive list of what can give goats soft poop, but it's some of the more common.
ETA: If this isn't from soft poop, some does when cycling do have quite a bit of discharge that gets gummed up on their tails. It would be possible for them to still be cycling this time of year