Try sprinkling some ground cinnamon lightly around seedlings as a preventative to damping-off -- it has anti-fungal properties, apparently. It worked for my seedlings...

@roxanna7

Oh, I wasn't aware about that. I just looked that up here, and you're right, it seems to help prevent damping off. I'll definitely buy a jar next time I go shopping.

How do you apply it yourself? Just at the time of planting, or only after seedlings show up? And how much should I sprinkle on?

Are you using a sterile seed starting mix?

agree with cear ... always start with sterilized media ... so you are sure there arent any pathogens to start with ...

and then 10% bleach all pots.. trays.. tools watering cans.. etc ....

its easier to avoid.. that cure a problem .... i think of it starting hospital clean ...

ken

https://tipnut.com/sterilize-soil/

John -- I have given up on seed starting now, but as I recall I just used the store-bought cinnamon jar with the shaker feature and sprinkled lightly right after I sowed the seeds. The amount sprinkled was visible, but not thick or heavy -- hard to describe. Good luck!

You can't kill plants by bottom-watering (although you could by over bottom-watering). For sure must be other reason for your problem.

Where are you?

What is the pH of your water?

(we can guess the second if you tell us the first)

Mad_gallica - nice adage but remember practically all municipal tap water in the US has something added to it to boost the pH beyond 7 and into the alkaline range. If it isn't already alkaline. This prevents it from dissolving copper pipes. Of course we don't know if OP is watering with tap water, well water, rain water, or river/stream water.

I grew Camellia seedlings for the first time this year and have found them a walk in the park compared to various other things I've grown. I hate to seem like a product endorser, but I know now to avoid "fly by night" seed starting mixes.* One I bought years ago was so loaded with composted manure a lot of the seedlings got damping off immediately. Absolutely moronic way to formulate a product like that - more moronic was me using it w/o reading the label. Might have been ok for vegetable seedlings but not rare trees and shrubs. I highly recommend getting one's hands on the TRUE promix - NOT the garbage sold at HD, Lowes, et al under that name. The one with both biofungicide and mycorrhizae.

https://www.greenhousemegastore.com/supplies/soil-and-soil-amendments/pro-mix-bx-biofungicide-mycorrhizae

No kidding, have not had anything damp off using it. Including ridiculously rare things like Nothofagus. I fertilized my camellias very lightly after they had fully formed their 2nd true leaf.

AND FWIW in the interest of full disclosure, I used the product above but added, in my concrete mixer, maybe 1/2 gallon of fir bark to 4-5 gallons of Promix. There is a Promix product that already has bark added but I decided it was more flexible to mix my own. The fir bark is actually easiest to buy at Petco, etc., as "Repti Bark". For, you guess it, pet reptiles.

* - and yes if you're wondering, I would say fly-by-night is anything other than what a professional wholesale nursery would use - and a lot of them would use the real promix!