Wet saw not cutting clean on porcelain tile

[jacoscar]

I just picked up a second hand Erbauer ERB337TCB. It came with three discs including the original. One of them was new, a Rubi Porcelanic TCR Super Pro (ref 31975).
I tried cutting a tile with the three blades and it chips with all 3, although slightly less with the brand new blade (see picture).
This seems to be a decent blade, but what am I doing wrong? I am going as slow as I can