Why does my program run very slow on MAC OS when built from version 5.3.4up when it runs normal speed like it should when built using 5.2.4f1?

I had a user complaining that since a few versions ago (when I switched to a newer unity engine/editor version), my program barely runs on his MAC. But when he loads up the one built from the 5.2.4f1 unity… it runs fine.

How can I fix this? The only change I notice is with the API for MAC being something I can select on the new Unity compared to the old one.

This is a screenshot of the same spot the user is saying is lagging on his MAC. There is basically nothing even going on besides me displaying text on screen with two sprites. It shouldn’t lag at all on even a commodore 64… not sure what is going on with Unity and MAC but it is surely upsetting. If I can provide any more details please let me know!
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