Thanks guys, the advice absolutely helped. Fortunately I didn't have to mess with the pots!
So to sum it up,
If your prints are getting misaligned/slanting towards a certain direction (left-right/front-back) check the respective motors for the following :
1) Pulley connected to the motor must not be grinding against each other, mine even has some residue due to the 2 surfaces grinding. Not good. Loosen the pulley, leave a gap between the pulley and the motor, re-tighten the pulley.
2) Loosen the motor, apply some pressure to push it downwards and re-tighten the screws. This gives the short timing belt more tension.
Thanks again for your input guys, much appreciated.