Garageband only recognizes one plugin of three installed
What plugin-type are they?
GarageBand will only use AU plugins, with a .component extension, it can't use VST etc. 

Each plugin type ought to be in its correct sub-folder - Components, Digidesign, HAL, VST etc

See
Interface types explained (VST, RTAS, AU, etc.)
Finding Audio Units plug-ins on your computer &amp;
How to Install plugins for Garageband - Add Audio Unit Filters to Garage band (AU)

You can force the AU cache to rebuild by deleting the cache file in ~/Library/Caches/com.apple.audiounits.cache while GarageBand is not running, then launch it again