Liam (3.5mo) does that too & I know it always happens on a day that he has had less stimulation the day before... ie spent more of his awake time in the pram, rather than on the floor, because we've been out & about. So my only suggestion is during her am awake times try & give her lots of tummy time, read books, change the place she is etc quiet often.
The last night sleep cycle is between 4 & 7am & it is the hardest one for babies/toddlers to actually pass through & thus you get lots of people complaining about the same thing, so you could say it is developmental too.
Re keeping in an EASY Cycle, well I just sort of go with the flow there, but our days tend to fit around toddler activities, so We rarely get a good EASY day.