I don't think there's any point in questioning them right now. They aren't gonna answer any questions and LE can't make them. They could only hold them a short time before releasing them anyway. IMO they've sold something that the buyer contacted LE about, that is in some way connected to the murders. I think that's how LE got the warrant to search the other trailers.
They can bring trumped up charges against them as they did with J Manley, then force them to submit to questioning in the grand jury. The same grand jury in which they've been questioning Manley and others.
If DeWine & BCI don't have questions to ask these people, after naming them as persons of interest, it would be very strange indeed. If DeWine has so much incriminating evidence against them that they don't need to question them, then he should be getting a warrant for their arrests.
DeWine, BCI and the rest sometimes appear to be doing their darndest to NOT solve this case.