To make fresh flowers last longer, cut the stems with a knife, NOT scissors or shears.  Clippers are two blades coming together and crushing the stems.  You don’t slice bread with scissors and you don’t cut your flowers with them either.  You are not in the back yard trimming the hedge, use the right tool for the right job and you flowers will be around much longer. 

Change the water every two days and keep them away from direct sunlight and heat sources. Your vase is full of stagnate water, It’s an old pond with dirty water. Give your flowers fresh water with lots of oxygen and they will be much happier.  Remember every time you change the water to recut the stems.