Nothing to worry about, these yellow blotches like this are quite common on cannabis leaves and seem to appear randomly and for no reason and at any time.
Not sure what causes it, but it might have something to do with chlorophyll not developing properly in those sections of the leaf.
The fact they have straight line/edge outlines would suggest it is not a spill of some sort or nutrient damage, as these two things will leave random shaped yellow patches without straight edges. The straight edges always seem to follow a leaf vein, and perhaps a blocked leaf vein is the cause?
Hope this helps,.........
Organoman.