You mentioned a tarp under the stones. Are really meaning a landscape cover which allows air and water in put stops weeds from growing out? If this is the case it needs to be changed. It is getting too much sun and the stones also absorb heat which also makes it hotter and drier. You could look for a plant or shrub that will tolerate the sun and drier conditions. But first check what was really put down.

Sorry, but your contractor did not solve your weed problem. He only delayed it for awhile. Next year weed seeds from grass, etc. will blow in on top of the stones and grow. And you will have weeds growing on top of the landscape fabric, instead of from underneath. Assuming of course, by stones you mean pebbles or gravel, rather than flagstone.

If you do a search on landscape fabric, you will see this mentioned again and again and again by homeowners who are frustrated that after all this work, they still have weeds! We all wish there was a magic bullet for weeds, but unfortunately there isn't.