Should i write my friends thank-you cards?

this past weekend, i went to the hospital b/c i thought i had appendicitis (turned out to be ovarian cysts). 5 of my dorm mates went with me at like 1 AM and stayed until almost 6 AM. they each visited me a lot, and were very helpful. i've thanked them a lot in person, but i feel like i should do a bit more...wold it be weird if i wrote them short thank-you cards?