I'm afraid we need more information in order to be able to help.

• Which version of the spine-unity runtime are you using (name of the unitypackage, also listed in Assets/Spine/version.txt)?
• Which skeleton component are you using (SkeletonAnimation, SkeletonMecanim or SkeletonGraphic)?
• Are you using special blend modes at the problematic attachment's slots?
• What are your atlas export settings in Spine?
• What are your texture import settings of the atlas textures in Unity?

Please be sure to check whether the export and import settings match, as described here:
http://esotericsoftware.com/spine-unity#Advanced---Premultiplied-vs-Straight-Alpha-Import