My DS was 2 in Oct, and his speech is coming on really well. However, I noticed today that he doesn't pronunce the 'f' sound. I've worried about sounds he's struggled with in the past, and he eventually picks them up, so hopefully the same will happen here. Just wondering if 'f' is one that other toddlers have struggled with, as I always thought 'l' and 'r' were the tricky ones...? Thanks in advance.