I see a lot of red spider mites in the summer when it's hotter. Although I don't grow croton, I think you did the right thing in wiping off the leaves. Do make sure that you "rinse" the leaves after about 30 minutes. Spider mites aren't supposed to like moisture so you could try misting your plant in the morning and see if that helps. I wouldn't automatically resort to using chemicals if you can resolve the problem with the misting.
