I got mine too, but now I am having trouble with Gallery. It won't open at all or sometimes it opens halfway. Is there something else I should use for my photos?
Try clearing the cache from the gallery app and also from the system.
For the app, long press and then drag it up to the top where it says App Info. From the next screen click on Storage then clear cache.
To clear the system cache do the following;
Put the Galaxy Tab S 8.4 SM-T700 in Recovery Mode by pressing and holding down the Home & Volume Up button together while pressing the Power button. Wait for it to get into the Recovery screen and then use the volume down button to scroll down to clear system cache. Once on it press the power button to select that option. After a few seconds it finishes then select reboot system.
After the reboot try the gallery app again.