Early wakings?

[Lilasmom]

Hi, my DD Lila is 18.5months old.  For quite awhile we weren't having any sleep issues at all.  We switched to one nap a day at around 14 months, and had been doing wonderful.  For the last few weeks, DD has been waking quite early in the am.  Anytime from 5-6:15am.  She used to always sleep until 6:45 or 7ish.  Which I was very happy with.  Also, her naps have started to differ in length quite a bit from day to day.  For instance, last week, she would wake after 50 min. crying, but I could easily go in lay her down and she'd go back to sleep from 30 min-2hours.  Then she'd have a random day where she'd sleep 3 hours.  Then the next day wake after 40 minutes and refuse to sleep any longer.  She goes down easily for her nap, and goes down easy for bedtime.  Also, this last week, she's been waking 30-1hour after going to bed for the night.  SHe'd wake crying, we'd lay her down, be quiet for a few minutes, then would be so restless she'd cry again.  Last night we had to go in 3 times.  I think she's overtired, but I'm not quite sure what to do.  This morning she woke at 5:20am.  We went in because she was crying, changed her diaper (having a wet diaper seems to botter her more lately), and laid her down.  We then did WI/WO until 6:45am.  She fell asleep, but then woke again at 7:20am.  So, I could tell she was tired this morning, so I put her down for her nap 20 minutes early.  She went right to sleep, so I guess I just wait and see how long she sleeps for.  I guess I'm just not sure how to go about this.  Should I be doing something different than WI/WO when she wakes early?  Should I then put her down early for her nap to try to prevent more overtiredness, or keep to the regular time?  If she doesn't nap long should she have an early bedtime?  Should I try to make a later bedtime?  As you can see I'm at a loss.  Any suggestions would be greatly appreciated.
Our schedule:
Wake:  No matter what time she wakes in am, we don't take her out of her crib until 6:45am
Breakfast 7:30am
Snack 9:45 or 10am
Lunch 11:30am
Nap 12am-1pm or as late as 3pm depending on the day.  (She seems to do best when she sleeps 2-2.5 hours).
Snack when wakes
Supper 5:00pm
Bath & winddown time 6:20-7pm
Bedtime 7pm

[imsmum]

Overtiredness was usually the culprit for night wakings, but with my dd an early wakeup usually was because she went to bed too late the night before.  i found that around 2 years my dd's sleep just naturally became a bit more variable and I think this variability can lead to overtiredness because it makes it hard to fall asleep when they need to at night.  If I sensed that the variability was causing some overtiredness this "formula"  really worked for her to nip any overtiredness in the bud. 

Put her down for her nap 20 to 30 minutes earlyand let her sleep to her normal wakeup time or no more than 20 minutes past her wakeup time.  That night put her down for bed an hour early.  i found that unless I did the slightly earlier nap time I couldn't get dd to go down early at night although the early night sleep was what was key to make up for any overtiredness.  If she wakes early from her nap you may want to move the bedtime another 15 minutes earlier so an hour and 15 minutes early 

[Lilasmom]

Thanks for the reply Imsmum!  Yesterday Lila napped for 2 hours (I had put her down 20 minutes early).  So, from 11:40-1:40pm.  She stirred at 50 minutes but went back to sleep.  I had to work last evening, but I explained your suggestions to DH, and he put her down at 6:25pm.  She went right to sleep and didn't wake until 6:15 this am.  So, she got about 14 hours sleep yesterday.  I wish she had slept maybe 30 minutes later in the am, but hey, 14 hours of sleep is pretty good.  Much better than waking at 5:20am!!  So,today because she woke early, I've put her down 20 minutes early again and she's gone right to sleep!!  Thanks again!  Just one question, when she wakes early in the am, should I just get her up?