I'm wondering if your soil is too heavy and retaining too much moisture? It sounds like it if it is actually mold on the soil. Is it kind of fuzzy looking? If not, it may be accumulated salt crystals. I copied the following from the eHow website:

How to Remove Mold From Dirt Mold Prevention for Indoor Plants

Things You'll Need
Clean, empty spray bottle
Distilled white vinegar
Water
Show (1) More

Instructions
1
Make sure the mold really is mold. Sometimes salts and other dissolved minerals can leave a white residue on the top of your soil which looks like mold. From a distance, the two look similar, but upon closer inspection, you can see that the mold appears fuzzy, while the residue looks more crystallized.

2
Identify the cause of your mold. Most cases of soil mold are due to overwatering. Mold requires a constantly moist environment to grow and thrive. A good rule of thumb for houseplants is to water when the top inch of soil has dried out. This means that the soil below this one inch is still moist, but has begun to dry out. This watering schedule will keep mold from having a consistently moist home. Another cause of mold is high humidity. If your home has excessively high humidity, try a dehumidifier, or add a fan to the area to circulate more air.

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3
Use vinegar to kill the mold. Mix your spray bottle with equal parts water and distilled white vinegar. Spritz this solution on the soil of your houseplant, covering the entire soil surface. Do not drench the area with the vinegar spray. You want to lightly mist the soil in about one to three passes, depending on the size of the pot. The vinegar changes the pH of the soil and kills the mold very quickly.

4
Retreat the soil. If after three days, your mold isn't completely gone, mist the surface of the soil again. Soil mold is often killed with one treatment, but persistent soil mold may require two treatments. Also, retreat any time you see more mold reappearing.

5
If after several treatments, your mold is not going away, consider using a spoon or small shovel to remove the top layer of soil which contains the mold. You can just scrape the soil off that has molded, or remove the top half inch and replace it with fresh mix. It is important to note that mold will continue to grow until the

But how would using vinegar affect the baby AVs? I don't want to kill them.. it's definitely mold as I know what salt deposits look like. I usually just remove the yucky soil, so I guess that part is OK. I wonder why some of the plants are molding and some aren't? I have a monstrous AF.. right now it has only 2 necks as I've split it once before (it had 3 and I got one off & got that growing on it's own roots), it's in a 1 quart pot and it's never molded. But the smaller pots seem to mold faster... and they're all right next to each other on the same window sill (west face, but heavily shaded AND is that frosted glass, so no direct sun).

Actually, I didn't read through it ... I just thought there might be useful information there to help. I wouldn't use vinegar unless it were highly diluted ... but, I wouldn't use vinegar or anything adding more moisture if the potting medium is already saturated. If they were my plants I'd un-pot them and repot using fresh, dry soil ... plus, I'd add a lot of perlite to the soil mix to help with drainage. I haven't grown AV's in a long time except for one single plant with no ID. I almost threw it out a couple of months ago because it was looking pretty pitiful but then I decided to repot it and I thought I'd experiment ... I use a mixture of a little soil and a lot of orchid bark mix for almost every single plant I grow so I re-potted the AV in that mix and it's done extremely well. I know a lot of people think they must water every week or two but sometimes that can be too much if the potting medium in use is too heavy and retains a lot of moisture.

This is my no name AV after I repotted it a couple of months ago:

Orchid mix, no kidding. And here I thought these things had to stay saturated - hence the self watering pots. Well, as dry as it is here, I just might need to keep it pretty wet..... sorry, thinking as I'm typing.

Heck, I can't even keep my orchids in orchid mix damp enuff! Big diff in our environments, huh, Lin? Our humidity was in the single digits last week, yikes....

Sheryl - That's my area all the time for the most of the year.. normal humidity is around 15-20% during the day & around 35% at night.

Lin - That's a very pretty AV! I have one very close like yours.. does your have a metallic sheen to it? I'm going to try & get a picture of it this weekend.

I should have known that, Toni - I can tell in the morning when my horses have their tails plastered to their behind from static cling, it's gonna be a drrrryyyy day!

Sheryl: Nope, African Violets and other Gesneriads don't need to stay saturated; in fact, keeping them too wet can cause root rot, fungus and decline of the plants. A lot of experienced Gesneriad/African Violet growers use a wicking system, with a piece of cotton cord or string trailing from a water reservoir through a hole in the bottom of the pot and up into the soil near the roots of the AV. This wick allows the plant to draw up just enough moisture to keep the roots moist without saturating them. Those self watering two piece AV pots do the same thing, the bottom reservoir pot holds the water and the unglazed top pot slowly draws up enough water to keep the roots consistently moist.

Toni: Yes, the flowers of this AV have a bit of a metallic sheen. I think it's a plant I purchased at either Wal-Mart or Home Depot a couple of years ago.

I used to kill plants by overwatering and keeping them waaaay too wet, so about ten or so years ago I started planting everything in a mixture of soil, orchid bark mix and extra perlite, a very chunky and fast draining mixture which works very well for me.

Single digit relative humidity. You have got to be kidding! When we have humidity that dips into the 50% range, we all think we have died and gone to heaven!!!!!!!!!! Ken

drdawg said: When we have humidity that dips into the 50% range, we all think we have died and gone to heaven!!!!!!!!!! Ken

Location Location Location. Y'all have water. We don't.

Yeah, there is that. But having just returned to the desert after 6 years in Tennessee.... I'm thinking I'll take single digits, lol.

Edited to add:
Thanks for the good info, Lin - I have been using the self-waterers, I guess it's a difference in perception - to me, that *is* pretty saturated!