Help, I'm under attack (maybe...)

[Herbsandveg]

I have some Chard seedlings growing in an approximately 2ft high plastic bag, and whilst on the morning tour of my ‘estate’ (ie ‘titchy back garden!’), I noticed that a white ‘mildew’ type substance had developed around the middle top of the bag. Due to my current ‘novice’ standing, I’m at a loss as to what this could possibly be, so I’d be grateful if anyone could tell me what might be happening, whether I need to abandon that batch of seedlings, or whether I can still save them by simply cleaning the ‘mildew’ away…

[rustylady]

Too wet, I think. Do you have drainage holes in the bag?

[Herbsandveg]

Too wet, I think. Do you have drainage holes in the bag?

Actually, I don't think there are. Silly me, I'll put some in tonight...Thank you!...

[Two_Sheds]

I have some Chard seedlings growing in an approximately 2ft high plastic bag,

What, like a carrier bag? A bin liner? Or a proper veg-growing bag?

Why aren't they in the ground? (is your estate too small?)