Unable to delete photos from my gallery on my Samsung Galaxy S5 - help! What do I do?

[AC Question]

Unable to delete photos from my gallery on my samsung galaxy s5 - help!

Up until today, I could easily delete photos but suddenly today I no longer have that option - all I can do is 'share' 'edit' and 'save'. What happened? I just returned from vacation and want to clear out bad and duplicate photos.