The skin damage is from humidity most likely, it happens a lot for me up in the tropics... Just a note, that maybe you know already but i feel drawn to share. If they are fresh cuttings, let them heal for at least a couple of weeks before putting them in soil to root. And when you do put them in soil, make sure it is bone dry for at least a month... It looks like your soil is wet and slow draining... If you use sand, make sure its gravel size...