I hope that doesn't happen to mine!
I'll avoid watering it for a couple of days, as suggested, to dry the soil out a little.
Fingers crossed!
I've never had a plant that's died for no reason. I've always come to the conclusion that I'M the reason! No matter how much research I do to find out how to take care of the plant, I just don't seem to get it right!
Mind you, I did have a small success once: I managed to grow a little advocado plant from the stone of a fruit I bought to make an advocado cheesecake. The plant grew to about 20cm and then suddenly lost it's leaves and dried up. So upsetting!

THe diseases i read about were ones that had just multiplied on the plant - nothing you can do about it.

You can get spray for greenfly. Sage like well drained soil, you prob only need to water twice a week at the most in the winter if you are keeping it indoors. My basil on needs watering once per week at the mo.