Electric UFH Dot and dabbed floor tiles - Tile Advice

[diynoobie]

I have recently moved into a house with both underfloor heating in the kitchen and bathroom.

3 or 4 of the kitchen floor tiles have cracked and i am fairly convinced they have been installed using the dot and dab method as i can hear a hollow sound in places.

I wonder if there is a product out there that i could pump into the free space and form a layer for the tiles to lay without ripping all the tiles up and starting again.

Thanks,

Ian