man i went throug smae prob, get some better soil, MG is great for tomato's not so much for herb.
you need to let em go for 2 day without water then lift bucket or use a scale, feel the weight, then water them and feel the difference try to keep that going.
also i was watering every day!, biig mistake as it caused water damage.
i also started adding a weakend nute solution during the second week. they reacted badly to this from the yellowing and burning. so i dialed my waterings back to once every other day and they have recoverd and all look much healthier since then. short answer every other day.
and the fact that they are seedlings means they are gonna need alot less water.
i water these 2 every other day, each get a a 20oz bottle of water that has sat out to let the chemicals settle. these girls are only 7 days old
the stems are a little weak but still doing decent, im watching the stem for rot and just giving em the 20 oz waterings, . hope this helps man, every other day worked best for me. ps they dont need nutes till 2 weeks earliest. soil/ h2o thats what they want right now