Why are tags from json loaded slowly on google maps?

Question

JavaScript

Hello, I have a map from Google, I use the jquery-ui-map plugin. Load markers from json file. When the page loads, everything is fine, all the markers are displayed quickly. Later I made 3 linked lists for the map using the jquery-chained plugin, and when I select for example "Region" in the 1st list, all the markers of that region are displayed on the map. While there were 5-10 markers, everything was fine, but as it was added to 60, when you select any item, the map began to load these markers for 10 seconds. Tell me what to do ...
PS If you need a code, I'll post it