Fixing bad floor tiling. Any way to add support under tiles?

[InTheBeginning2007]

A friend, who assured me he knew what he was doing, put down tiles on my kitchen floor and although they are neatly down, he used adhesive put in blobs on the tile, then put it on the floor. Needless to say, some tiles don't have much support under them and I cracked one by standing on it.
The grout is not put in yet, and I was wanting to know if it is possible to poor something in through the gaps to fill the voids and add more support under the tiles. Self leveling compound maybe? It is on a concrete floor.

Thanks.

 

[lancenotalot]

I'm afraid it sounds as if they will need to come up and be relaid properly.

 

[InTheBeginning2007]

I'm afraid it sounds as if they will need to come up and be relaid properly.

If that is the case, I think I will just grout them and when / if they crack, I will cut out the cracked tile and replace it.