Did you purchance fertilize them?
It is good that you didn't fertilize the baby seedlings. Fertilizing very young seedlings before they have grown at least their first set of true leaves leads to what is called damping off. There are also other reasons for damping off such as rapid temperature change and too much water. Your plants in the pic from what I can see look OK except for being too close together. This isn't your fault but personally I do not like those peatmoss filled seed starter dodahs for a number of reasons which I will save for a later day
I will try to explain tomorrow AM
In my opinion the seed starter kits only redeeming quality is their ease of use. They are made of peat, are acidic and lack the much needed micro nutrients important to rapidly growing seedlings. They retard root growth as you have seen in your corn and sunflowers. Imagine how much more those roots would have grown if they weren't restricted.. They are supposed to rapidly deteriorate but I have dug them up a year later still in one piece. The kind you have with the little bag aren't quite as bad but still leave a lot to be desired. Also, in my experience with them I suffer a much higher percentage of damping off. Why? I'm not sure but I think it is related to the manufacturing process of the kits. There has to be some sort of liquid involved to shape the pellets, the pots or whatever shape the kits come in. I suspect it involves liquid chemical fertilizers but that is just a guess. If you really want to grow you herbs and many other vegetables from seeds here is how I do it. For herbs; Obtain from your nursery some of those shallow 4 pack or 6 pack containers that plants come in. Get a seed tray that does NOT have holes in the bottom. Get a bag of premium potting soil and a bag of premium compost. Make a 50/50 mix and put it in the plant containers until almost full. Put the plant containers into the seed tray and water slowly and thourghly until the water comes out of the bottom of the plant containers and is completely soaked. Sprinkle about 6 of the tiny herb seeds into each of the 6 pack containers and GENTLY press the seeds into the soil. Then get a very very small amount of the dry mix and lightly sprinkle it on the seeds. The moisture will wick up and wet the soil that has barely covered the herb seeds. Put them in a warm place with ventilation. About twice a day until they sprout and have been up 4-6 days spray a little water on them to keep the top 1/4"-1/2" slightly damp. After they have been up about a week stick your little finger into the opening at the bottom of the container. I will probably feel dry. If it does then put about 1" of water into the seed tray and water the 6 packs from the bottom up until the top is wet. Pour out any water remaining in the tray Do not fertilize until you can see the second set of true leaves forming and then only lightly. This method works well with herbs, cucumbers, squash, mellons etc I do tomatos, peppers, eggplant a little different. Remember, you can't water too much but you can surely water too often.
Some of the stuff you can probably get for free such as the 6 packs and starter trays from your local nursery. I don't know how many plants you intend to start but I can't imagine spending more than $20. Let me know what all you intend to plant'. I have forgotten where you are located
For herbs, container gardening is great. You will also find the seeds you want online. I agree about about GMO's but we may disagree about organic seeds. The effect of non-organic seeds over organic is miniscule and one never knows how organic the seeds really are or how old they are no matter what the producer says. The only sure fire way is to grow your own.
In my experience the biggest failure in growing plants with little tiny seeds is that they are planted too deep. Once they have germinated the old squirt bottle 2 or 3 times a day works miracles. Like lettuce for instance. You don't bury them at all, just firmly press them into the damp soil
A classic example of damping off and I suspect there was fertilizer involved. Remember that you can't over water a plant but you can water too often. The roots of plants are just like our lungs, they need air, otherwise they will basically drown and/or rot. I suspect also that you showed those little seedlings too much love
