Why has my 7mo gone from sleeping through the night to waking at 4am?

[missbumpy]

She was brilliant at sleeping through from quite a young age (2 or 3 months) but just in the last few wks she's started waking anywhere between 4 and 6am.

I've tried blackout blinds. I've tried putting her to bed later. I've tried putting on less clothing/blankets. I've tried introducing solids in the evening (she was only on lunchtimes before).
Nothing works!

I know I should probably try to get her back to sleep without feeding but TBH breastfeeding her seems like the quickest and easiest solution at 4am!
Help! What's going on?

growth spurt maybe??

Either a growth spurt or maybe it's too warm in her room, even with the blackout blind (this has woken my DS up a few times, even thought he sleeps with nothing on but a vest and no covers at all, the loon).

Thanks. Could be a growth spurt. She is looking quite enormous at the mo! And she seems to have developed a lot of new skills all of a sudden (eating solids better, rolling, trying to crawl, babbling...) so maybe all of her exciting new developments are keeping her awake?
It has been quite warm the last few nights but this has been going on for longer than that so not sure that it's heat related.
I'm trying to keep her awake longer tonight in the desperate hope that she'll sleep for longer.