About 4 weeks ago, while on vacation, I purchased a small cactus and succulent. I would put the cactus at about 2" tall and the succulent at 3" tall. I have no idea what these plants are and I'm afraid I may be under or over watering them. Already, some of the thorns on the cactus seem to have turned very brown (previously they were white) and the succulent seems to be drying out (one leaf even has a big brown spot on it). Can anyone identify these plants or advise me as to how to take care of them? I currently have them inside sitting on a windowsill and watering about once a week, the succulent gets twice as much as the cactus. Thanks :) Edit: It appears that the succulent may be a Crassula Argentea, can anyone confirm this?