I'm very curious about the dietary changes as well.
However... I have a fabulous group of nappers here too aside from my own son (isn't that always the case).
I have all toddlers 13-19 months including my own son. All of them arrive between 6:45-7:30 and my 7:30 arrival's parents commute from about an hour away and my daycare is halfway to their work and right off of the highway which makes it convenient. This means all of these kids have been up from at least 6am before they arrive to me. I would say almost all of them are kept up later at night so they are still needing a morning top up nap here as well as an afternoon nap.
It can get frustrating because I feel like most days we don't get to do too much as a group someone is always sleeping. I have tried making morning nap only an hour 8-9 and I am always waking the kiddos up. Sometimes one is so miserable I have to put them back to bed for another half hour. During morning nap, I spend the time with my own son, clean up, prep lunch. We have lunch here at 11 and afternoon nap is 12-3 and they all STILL need to be woken up at 3!
I don't get it! Not that I am really complaining but I understand your situation.
I would suggest doing a morning nap again for this one and keeping it 1-1 1/2 hours then using that time to do crafts or another activity.
I have also okayed with all my parents that if their child is still asleep going out into my backyard with the baby monitor on with the other children for playtime outside so that the others dont miss out.