I'm definitely no expert, but I'm looking at your power graph, and here's what I think...
You seem to have nearly as much energy on your latest ride as your six week average. Everything above about 90 second duration is virtually the same... "10-15 watts less" is only 5-8%. In a race, 5% is everything. But in a race, you'd have much more motivation to push yourself. If you're not a morning person, the fact that you're getting out at all is commendable, and improving your performance that little bit might only require a little mental effort.
Clearly, you didn't peak as high, and there is a significant difference for all durations below one minute. But I think this graphic gives a skewed view (hey, that rhymes!) of your overall performance. If you're trying to match your previous (afternoon/evening) instantaneous or short duration max output, there's obviously some work needed. But I wouldn't be too upset over the whole-ride average.
One idea, maybe you've already tried?... Before starting your ride, do some quick, high intensity warmups. Dynamic stretching, jumping jacks, run in place for a minute, something like that. Maybe even spend five minutes on stuff aimed at getting your heart and lungs up to speed. I don't practice what I preach here, usually just hop right on and start riding. I wonder if it would make a difference though.