Before it gets too cold, bring your house plants back indoors. Check the leaves for diseases. If you bring a suffering plant indoors you run the risk of infecting your other plants. Hard as it may be, the solution may be to just throw them away.
Once your healthy plants are back indoors and have adjusted to their low light indoor climate, it is normal for them to shed leaves...so don't worry.
Tempted to add fertilizer? Indoor plants need to naturally adapt to less light, so wait until late winter to fertilize.
