I really cannot tell from the photos (although someone else will certainly have a better eye for this than me). However, if you are watering at night and/or are getting the leaves wet, you are increasing your chances of mildew.

Good luck.

Hi
To my eye the picture does not seem to support the diagnosis of powdery mildew. Mildew is unmistakable in
appearance. The leaves will seem to have been sprayed
with a white powder. Just a few leaves or the whole
plant if bad case. Appears to me from the picture to
be mites or aphids. I would spray with a combo insect-
icide/fungicide to be on the safe side. Plants appear
to be cramped for living space which invites disease etc.
Hope this helps.