Firstly, these gulls seems to be taken quite recently (Sept/Oct, at least when looking att the 2cy bird (pic.3). When looking att the two juveniles/1:st winters, the overall colour - brownish reddish or rusty tone to the plumage is better for Yellow-legged sicne Herring usuallyare darker brownish or brownish -grey in plumage tone. Gull nr 2 shows good features of Yellow-legged, such as unmarked belly with breast and flank markings.
Head pattern - whitish with dark 'mask' is good for Yellow-legged. when looking at the tertial pattern on that bird, they are rather similar to the average Herring, with pale notching (upper ones more worn) but not reaching the greater coverts, which is not the fact with all tertials on this gull as can be seen. Not really a full proof feature, since some Yellow-legged (and Caspian Gull) shows pale edgings reaching the greater coverts in a similar fashion to Herring Gull. Gull nr 1 is a bit trickier due to angle and one can understand that it might be identified as a non- Yellow-legged but it is most probably a Yellow-legged (not that Herring is unrecorded in the area),on overall colouration, bill shape, rathe unmarked whitish head with a dark 'mask' and relatively unmarked lowe breast. . The 2cy bird might also be tricky, perhaps because of the bill shape and thick sturdy short legs. However, all gulls vary and some can take you by surprice. 2cy Yellow-legged are usually more advanced in plumage compared to 2cy Herring but there are exeptions of course since variation in moult and timing has to be considered. Yellow-legged for this one as well.
Check around here:
If you use the traslation on this site, which is made by gullfriends of mine, it´s a very good site with loots of exellent pic. and good wordings!