i have had this problem with corrinader as well. Apparently they like poor soil which is well drained. I planted a load in a big wooden box that i made which was filled with pure potting compost.

They came up really well to about 3 inches high with lots of bushy leaf growth and then just withered dont know why.

Now i have dug a round patch on my lawn and planted some there, in full sun exposure and there are really bushy, lush growth, and really scented. i put them out last year, used them up and they went thru winter with the frost and snow and this year they are still growing. that has never happned to my corrinander before but they are still growing. I try not to let them go to seed, so keep using/pinching the leaves once they get too high