Black magic itself has different signs, but once you ask about signs of black magic on your husband, you are specifically asking about the signs of the black magic that is only affecting your husband. That is true that sometimes sorcerer does black magic to the only husband to make couple life miserable. These are mostly revenge-type spells to hurt someone. So these are the most common signs of black magic on husbands.

1. The husband starts fighting without any good reason.
2. Husband starts noticing each small movement of wife that he does not like.
3. Start controlling wife.
4. Disinterest in intercourse.
5. The husband becomes sick and once he stays away from the wife he feels good.
6. Starts forgetting the name of his wife.
7. Spending time more out of the home.
8. Having affair with other girls.

There may be other signs, but you have to consult with an expert right away after you feel something is wrong. Sometimes jealous people do normal magic spells that may different or have different signs. Different types of spells are having different signs and different purposes. You can read here all symptoms of black magic.