Beginner Gardening: thinning and drying only at base of stem, 0 by _Mai_

_Mai_ wrote:
a while back i planted some african daisies from seed and noticed that while some were doing just fine, others in the same growing conditions were drying thinning at the very base of the stem where it meets the soil. the leaves then obviously wilt. is this something to do with watering? i think i read somewhere that if you overwater that the base of the stem can weaken at the base and the plant will fall over, but these seem to be dry and stiff where it thins out, not soggy and flimsy. not quite sure why, but it's highly annoying and i feel helpless to do anything about it.
i even have one that's producing buds while others around it are dying, how is that?