Kitchen usually draws water from the main, so if you have low pressure at kitchen, you have to check your filters or syabas.

Wheres bathrooms and toilets get water from tangki.

Two different problems.

If the pressure at kitchen is affected by bathrooms and toilets, then you have to check if your kitchen is taking water from  tangki, or you bathrooms are taking water from main ! Likely you might have a modified piping.