Google Map red markers take a few minutes to load

Hi,

I have this site https://activeshipyards.com/ which loads OK when you click it but I have to wait a few minutes before the red markers appear on the map. This results in slowing down the search process and site gets slow in general. Once the red markers appear the speed seems to be OK.

I have seen other sites on the internet that use maps with markers but they load super fast. Once you click on their site everything loads fast, no waiting!

I have added WP Fastest Cache and Far Future Expiration Plugin, did the settings as read, this is why the site loads OK. I only have problem with the red markers that are too slow to load.

Any suggestions?

Thanks in advance