Great pics Tracy.
Heads develop as the dog matures as well, some slower than others.
Lotus has a fab head and stop. Stops can deepen as they grow too as hers did. She has a huge head, it's really hard to photograph clearly but she is a good example of an apple head.
You can see her stop is v deep in this.
Leilanis head is maturing (slowly like her auntie) but she has a good head for a pup.
On young pups their stops are well defined 8-9 weeks is the best time to tell according to all the experienced breeders I've spoken to. Remember they don't stop maturing until at least 18 months so it's a long wait. What I will say though is if you aren't sure don't buy, it's a long time to be disappointed.