Leaves on some plants dying!

[RobinB]

I have started to notice some plants with dry, crunchy leaves and stems dying from the bottom up. There is not any discoloration or yellow spots anywhere, if anything they are darker green. Then I looked at the leaves above those that had dried up and noticed some that were halfway okay and halfway dead. There seems to be a fuzz on them. Is it mold, late blight, ? I do have some thrips and spider mites around, but this doesn't look like insect damage. I checked under a 30x hand lens and didn't see any insects.

Any help is appreciated. So far, the middles and tops of the three or four affected plants seem okay (I have removed and disposed of the dried up leaves and stems) so I hope that I can get a handle on this before it spreads.

Here are four photos. #2 and #3 are the two sides of the same leaf.

Thank you!
Robin