It could just be that he has entered a developmental leap - there is a language leap at 21 months (obviously slightly earlier or later for some) which can throw sleep off like any development can. I remember posting about my DS suddenly going off track with his sleep at this age too. I think the phase lasted a couple of weeks so perhaps just hang in there for now and the routine will go back to how it was before the leap?
If you changed the cot quilt maybe try switching it back and see if that helps?
You could also try some additional physical activity before BT. At this age (and for a long time) mine did much better with lots of gross motor before BT, rather than having that extended BT we put our energies into setting up activities for after dinner so he had the opportunity to use up the last of his physical energy. We did:
- toddler band, all of us marching with instruments and singing, walking from family room to kitchen and back, many many times. He often started jogging.
- chase and tig/tag
- Mr wolf (more chase)
- wrestling with Mummy (controlled wrestling)
Another thing I often do during phases of not going to sleep at BT is to do the wind down and put down later, it doesn't necessarily make actual sleep time all that much later, it reduces how long you are going in and out for.
hope this helps some
