The three that are working use Google for their SSL. The two that aren’t use Let’s Encrypt.
Let’s Encrypt changed their chain of trust earlier this year and looks like Android 6 doesn’t have the root cert in its certificate store and therefore the certs for the sites that don’t work cannot be trusted/validated. This is my guess 
I bet if you go to https://api.agify.io in the browser on the Android 6 device you’ll get an SSL error.
I have to ask, who still uses Android 6? 
It was released nine years ago.
Sources
