Exposure Issue

From my corner of eye, i see some strong "vinieting"  ,  to fix it   in lightroom, it can happen of using cheap lens 

Those both look a little on the dark side for me too. Have you checked to make sure your monitor isn't overly bright recently? They can sometimes get out of whack over time. You really want flowers like that to pop and both shots look a little dull. It's hard to give any other suggestions for improvement as the example images you've provided are tiny. But, yes, brighter would be good without losing the nice deep shadow areas.