Vaginas.....

[helle]

Too much sugar can affect things down there for me. If I have a sugar binge you can almost guarantee I'll wake up the next day with thrush, or just be totally uncomfy down there and ick. Things like cool drink are pretty bad. I don't have them often and definitely not on consecutive days!
Maybe try cutting some out a bit and see what happens? My naturopath always says "healthy gut, healthy everywhere else"

[Phteven]

The bodies natural Ph is a little acidic. Try putting some vinegar in their bathwater and it might help keep the flora balanced.

[Eenee]

I'd also recommend to stop using the flushable wipes.

[Rouge]

I would take them to the GP. Not wait till the next time you go. Sounds like a yeast infection. Which can end up being very painful if left unattended.

[BellyBelly]

It can be a combination of all of these things. I'd cut out all bubblebath, bath salts, wipes, soaps - you only need water or you can mess up the balance of good flora. Antibiotics will also disturb the balance of good and bad bacteria. Obviously wiping front to back is very important. Thrush/yeast infections love sugar, so cut out that where you can and lots more fruits, veggies, pure juices that you make from home. You can get kids probiotics from health food stores or chemists and also up the garlic. Apple cider vinegar in the bath is definitely a good help. It will take time to build up good bacteria again so it will need a little time.

Sounds like an anti-fungal is needed for relief, but you need to make lifestyle changes to make sure this doesn't happen again as creams are only a bandaid fix.

Check out this article for lots of info. Thrush / Yeast Infections - Take Control of Thrush

[Rouge]

And also one of the biggest causes of dermatitis in little girls is not drying themselves properly after bath/shower or after urinating.

[Phteven]

If they are wearing underpants overnight maybe you could ditch them. I have to use the term let it breath but getting some fresh air down there is good.