Generally the drakelets will outgrow the ducklets by 8 weeks. Also, drakelets will have much bigger feet & a larger, heavier shaped head.
It's hard to tell by your picture but it looks like you have 4 drakes.
I can't really tell much about the one laying down w/it's back towards us. Is it the same size as the other three close to it?
The two laying down facing us are definitely drakes. Try to get a closer pic of them w/their feet showing and standing in profile if possible.