Very hard to tell. Perhaps too much sun -- move to dappled shade if they are struggling.

Or, inconsistent watering -- too much or too little.

Little citrus seedlings can be a bit temperamental at first.

What are those brownish granules in the soil?

Hi and thanks for the feedback. The brownish granules came with the potting mix, which had some perlite in it. I did not alter the mix at all, I just bought it from the store. Just odd that some seedlings seem to be ok... really don't know what to do. :(

The cause is most probably Rhizoctonia solani. a fungus that lives in wet soils as sclerotia. This problem is very common with young seedlings, when the medium is kept wet. When watering new young seedlings, water only in the morning, and then put the plant in the sun so the soil surface will dry. Doing so greatly helps prevent the fungus. Also the containers are much to large for such small seedlings. thus keeping the soil surface wet too long. You can also purchase a fungicide at the nursery to kill this fungus.

Hi Silica, thanks for the response. Any suggestion for a good fungicide brand?

Just tell your nurseryman you wish to purchase a fungicide for stem rot in young seedlings to control Rhizoctonia. There are many brands.

I heat my soil upp to 212F to kill all pathogens before using it for seeds/seedlings.

Steve

They may need some fertilizer. Osmocote is good for seedlings because it is slow release.