For a 45 minute ride first thing in the morning, food and energy stores shouldn't be an issue, unless you're doing something horrendously wrong with your eating habits, like outright starving yourself. For ~1 hour rides in the morning, I don't even bother with coffee before leaving.
It's also worth noting that the upper line isn't your average, it's your *best* performance for a given duration over the selected time frame, so for that 18:45 mark, you're not 16 watts off of your average, you're 16w off of your best. This is not something that I'd worry about - just keep at it.