GLTFLoader: specularGlossinessTexture is sRGB.

examples/js/loaders/GLTFLoader.js

@@ -2240,9 +2240,10 @@ THREE.GLTFLoader = ( function () {
 
 			}
 
-			// emissiveTexture and baseColorTexture use sRGB encoding.
+			// baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
 			if ( material.map ) material.map.encoding = THREE.sRGBEncoding;
 			if ( material.emissiveMap ) material.emissiveMap.encoding = THREE.sRGBEncoding;
+			if ( material.specularMap ) material.specularMap.encoding = THREE.sRGBEncoding;
 
 			if ( materialDef.extras ) material.userData = materialDef.extras;