It's like a time-bomb in kittens which explodes when the weather changes. I thought since Blackie had got past the disease in her youth (with Graphites 50m and Causticum) and had one surviving kitten from her previous set, this set would be safe. But I was wrong - kittens born just before the onset of the monsoon are much weaker than those born after or a month before.
It is just a wrong time to mate - mating should have been triggered earlier than that for a normal healthy cat to have immune-developed kittens survive the monsoon changes. I've observed very sick or alcoholic men and women have a similar poor timing to their mating, giving birth to children who, if they survive, have lifelong problems. In fact, I've seen the most diseased men get amorous during the worst, stressful times, get drunk before weather changes and collapse on the street.
I'm guessing that children born during the monsoon (gonorrheal and cancer time) and before the winter (syphilitic and tubercular time) are full of problems as well - the gonorrheal miasm preventing proper nutrition and hardening glands; and the syphilitic and tb miasm leaving respiratory, liver, kidney and bone diseases growing in them. I wonder if governments should make a rule: only mate/baby-make between Dec-Feb and Apr-Jun to save on the future healthcare costs incurred by your children!:) This might be the reason we have 'wedding seasons' in India ... unspoken pressure to breed healthy.