Help!!! Why is my wordpress sites downloads the php files instead of loading it

Hi! I’m not new in WordPress, I know basic knowledge about it, but I came across these problems where 3 of my WP sites downloads PHP files instead of loading (i.e. when I try to change permalinks, activate/deactivate plugins, etc.). Also, those 3 sites are not redirecting to https even after I installed SSL (when you try to access it). They only redirect to https if: you click some articles; images; and categories.

By the way, I’m using:
– WordPress ver. 4.7.4
– LAMP Module (since I have multiple WP sites)
– Digital Ocean’s Droplet (I migrated them from Bluehost)

Hope anyone here can help me with this