Deleting photos on one device doesn't remove them from other synced devices

Brokenwing18 wrote: … If all devices are synced shouldn’t deleting photos off one device remove them from the others as well?

Of course! So what's going on? We can't see your devices, of course, so here are some questions that might help us:

1. Have you checked to see if the Apple Account is really really the same on the iPads and on the iPhone and at iCloud.com?
2. Do you have “Optimize Storage” checked in Photos’ Settings on your devices?
3. Do you see the "deleted" iPad pictures at iCloud.com? What's there?
4. Do you have more than 10% free storage on your iCloud account?
5. What is your storage on this iPad? At Settings>General>iPad Storage, my phone says 50.5 GB of 128 GB used. What does yours say? Do you have more than 10% free storage on your iPhone and the new iPad?
6. Have you had it work normally before, or did this just start? Can you think of anything that changed that might affect your device?

Have you tried a forced restart? 

Force restart iPhone - Apple Support

Force Re-start iPad

This is different from a simple Power Off. I had to continue holding the button down past the "slide to power off" message, and then I released the button only after  the Apple Logo appeared indicating a re-start. 

Let us know…

if you use iCloud Photos on all of the devices, changes made on any one device reflects on all devices. You may need to connect the iPad to power to have sync kick off.