I decided to go the css way and fixed the grids.

I’ve tested it with the ones I’m going to use: Big Grid 3, 4 and 6. Not sure if the others work.

Here is the css code if anyone has the same problem.

.td-big-thumb .entry-thumb {
height: 100%;
width: auto;
}

.td-medium-thumb .entry-thumb {
height: auto;
width: 100%;
}

.td-small-thumb .entry-thumb {
height: 100%;
width: auto;
}

This css fixes some block problems as well.
.td-module-image .td-module-thumb .entry-thumb, .td_block_14 .td-module-thumb .entry-thumb {
width: 100%;
height: auto;
}