I noticed that since my upgrade to ES 7.5.0 searching became real slow using the searchbar. Before my upgrade from 5.6 to 6.8.0 to 7.5.0 the searching hits were shown pretty fast while I was typing my search word into the searchbar. Now I often get a spinning wheel. Besides that when I use the Knowledge Base search the same searching hits are shown pretty fast. With ES 7.6.0 the problem still exists.
Did you notice similar behaviour?