Ok - that changes everything but still details are critical
What are your setting for iCloud in the Mac System Preferences and in the Photos preferences and on each IOS device
As a wild guess with no details it sounds like you may have iCloud Photo Library set and if you do then you library is on iCloud and any changes you make on any device including additions, deletions and edits is reflected on all devices as documented - if you are using ICPL then the solution is to check the Optimize photos on devices with limited storage
LN