Did you take a photo that shows the stem (stipe)? Initially looking at the colour I thought they might be omphalotus nidiformis, the luminous fungus. On closer inspection the caps are the wrong shape. The front cap on image 1, the one with the little fungus fly (Tapeigaster luteipennis) on the left edge appears to have a dusting of white spores on the back section. I'm wondering if they might be an Armillaria. I can't see the cap surface clearly enough, which if Armillaria would have a 'gritty' look about it. The stipe would have a stubby ridge, ring on the upper half of the stipe and the stipe itself would most probably be lighter in colour about that ring and paler below. Sometimes there's a hint of pink in the gills (lamella). If you have the opportunity to have a closer look or better still additional photos I may be able to give you a definite identification. An impressive group!
The caps certainly have a gritty look to them, but I will have to do some more investigation to get a good image of the stipe. Is there a facility to submit additional photos of an existing sighting?
Having comeback and looked at this sighting I feel confident to confirm it as an Armillaria sp. though unfortunately still not able to put a species name to it. Good recording.