The tang it that picture looks to have bacterial issues, most likely secondary to velvet, brook, or possible a whole host of other issues. If it were me... I’d be looking for a new LFS or possibly mail order, if the majority of the fish at your LFS look like this one [emoji20]
If I did bring that particular fish home- I’d have a freshwater dip waiting, followed by an acriflavine bath, and a QT that’s been pre-dosed with metroplex, kanaplex, and a low level of copper... and begin slowly raising to therapeutic over the next 48 hours. The freshwater dip would tell if he had flukes as well. If so, it would be necessary to replace the next metroplex dose with general cure. Same thing, 6 days later. With all of these meds... I’d have to add an extra air stone and maybe a second powerhead to ensure ample O2 exchange.
Even after all that...and that is a lot of meds to dump on a fish at once...there is a very good chance that fish would not survive.