Please suggest a specific antifungal treatment.

Sorry to say I don't know what this is, have never seen it before. I'd send photos to Glasshouse Works & ask to return it for a refund.

What kind of certificate are you referring to pls? Know of Glasshouse Works, but not any certificate?

What kind of pesticide did you use? Is that why they look so wet? Pardon me, but if is this bad & you think it's spreading I'd return it or throw it out.

You could struggle to try & save it, risk spreading to your other plants, but why risk it? Moonshine is neither rare, nor expensive, so sorry, but I'd toss it.

I don't care about this plant in particular, but I have a large collection and I want to use antifungal to keep this from spreading to those. It's wet because I rinsed off the dirt to see the fungus better. These leaves and the whole plant are going to be thrown, but I'm mad that I bought it from a business, and it bright this into my collection.

I think it's a risk to buy anywhere. they send along a certificate that their plants are free of invasive disease and pests, and that the nursery had passed inspection.

Anything I can spray on the plants that are showing no signs?

I personally don't know of or use anything like that. Hopefully, others will respond. You didn't answer if you contacted the Vendor.

The only antifungal I know is cinnamon, used by some folks to combat fungus, I learned it from the Orchid Forum. I use it sprinkled on fussier succulents' roots sometimes to stave off root rot. Pls read up on that. Perhaps search "using cinnamon as antifungal". I don't know of preventative measures, other than isolating the offenders to other rooms, sorry.

I've previously gotten good plants and bad customer service from them... I'm reluctant to even try contacting them.

Always when using pesticides do so after the specific disease or pest problem has been identified, a product known to address that particular occurrence has been selected. Otherwise you are likely to be wasting your time.

If your problem is in fact basal rot of Sansevieria it is caused either by overwatering or exposure to temperatures below 41 degrees F. There may be some potential for getting improvement from dusting affected parts with Sulphur (when the damage is fungus related) but in general once the base of a particular specimen becomes rotten the party is over. With any cuttings attempted having to be done using portions that are clean.

I consulted with a master gardener at the local greenhouse. She thought it was a bacterial disease and recommended that I get the affected plants outside into bright sun for the summer and keep them dry. I also got Daconil for the unaffected plants that are nearby. Thanks for all the suggestions.