You know what, for the past 5 nights, DS has been waking up after the first and second 35 mins at night, and then just tossing and turning till midnight (I only monitor until then as I need to sleep too!). Usually, he only does this when he is overtired. However, due to being ill and all, he has been having super short A time. Therefore, I can't imagine him being OT! He is definitely not UT either cos he goes to sleep within the perfect 15-20minutes. When he is OT, he goes to sleep immediately.
And when he did it again last night, DH just said "Maybe it's developmental". I said, "You think? Again? counting all his developmental leaps he should be a teenager by now!!!". So yeah, I just don't know! I am just going to wait till he gets better and see what happens. If it continues then I am seriously going to cut his nap or do something!
So yeah, could DD be going through a developmental leap? Based on how DS is reacting right now, I would not disregard it :X
Update: I forgot to add that DS has his last 2 molars (upper) coming in too. One has broken through (tip) and the other not yet. I gave him ibuprofen for a few nights but it was no different to the nights that I did not give. So yeah... more developmental leap possibility.