There is a rent or lease agreement signed between the landlord and the tenant which is supposed to be adhered to by both parties,. If the agreement contains a clause which says that in times of natural calamity the tenant will not pay rent, then it is Ok, otherwise the tenant has to follow the agreement in letter and spirit.
If any month the shopkeeper earns much more than his average, is he supposed to pay extra rent ? No, of course not. Similarly business is all about profit and loss and it is a dealing between two parties. If the govt wants the landlord should not take rent from the shopkeeper it should also tell the shopkeeper to not take money from the shoppers!.. There is no end to administering such 'platonic' justice. Anything half baked is eventually detrimental to the society. ZA Bhutto tried such gimmicks for earning popularity and harmed the society.