AndroidStudioのbuild.gradle(app)にて

build.gradleでエラーが出て，実行することができません．以下にbuild.geadleのdependency{}の内容を記します．

dependencies {
    implementation 'com.android.support:support-v4:26.1.0'
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support:design:26.1.0'
    implementation 'com.android.support:cardview-v7:26.1.0'
    implementation ('com.facebook.android:facebook-android-sdk:4.29.0') {
        exclude group: 'com.android.support', module: 'support-v4'
        exclude group: 'com.android.support', module: 'appcompat-v7'
        exclude group: 'com.android.support', module: 'design'
        exclude group: 'com.android.support', module: 'cardview-v7'
    }
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    testCompile 'junit:junit:4.12'
    implementation 'com.squareup.picasso:picasso:2.5.2'
    implementation 'com.squareup.retrofit2:retrofit:2.3.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
    implementation 'com.squareup.retrofit2:adapter-rxjava:2.1.0'
    implementation 'io.reactivex.rxjava2:rxjava:2.1.3'
    implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:1.2.10"
    implementation 'com.jakewharton:kotterknife:0.1.0-SNAPSHOT'
    implementation 'com.github.d-max:spots-dialog:0.7@aar'
}

エラー内容は以下の通りです.

All com.android.support libraries must use the exact same version specification (mixing versions can lead to runtime crashes). Found versions 27.0.1, 26.1.0. Examples include com.android.support:customtabs:27.0.1 and com.android.support:animated-vector-drawable:26.1.0 less... (⌘F1) 
There are some combinations of libraries, or tools and libraries, that are incompatible, or can lead to bugs. One such incompatibility is compiling with a version of the Android support libraries that is not the latest version (or in particular, a version lower than your targetSdkVersion.)

https://qiita.com/najeira/items/ce774acf14a0cedf8f7a
上記の記事を参考にしてみましたがエラーが出続けます．
また，このエラーはfacebook-sdkを追加した時から出ています．

何か解決する手段はないでしょうか．
お忙しいところ恐縮ですが，よろしくお願いします．