Gymnopilus spectabilis ...

[BubikolRamios]

Have 2 more finds like this, with white base, maybe one find with glimps of ring,but not sure, all max. 25 mm(not yellow any more, brown). Not sticky.

So, Gymnopilus spectabilis lately became Gymnopilus junonius, which should have ring, Local. desc. of that says 5 -15 cm cap diameter !?. Does not mention white base.

Neighbours of that on image, not much bigger, getting whitish. Mostly Fagus.

?

[abeja]

This can’t be Gymnopilus junonius.
Young mushrooms of that species always have a velum, which leaves behind a ring - in very old mushrooms, the ring may fall off. The "babies" are significantly larger than your small ones. The description on the local website is correct.
For comparison, fruiting bodies of G. junonius that I found years ago on an oak stump:
Notice the size of the young mushrooms compared to the leaves. Fully grown here: cap diameter up to 20 cm!!! Stem diameter 45 mm!

Gymnopilus junonius_11-2014.jpg

Gymnopilus junonius_Stielbasis_11-2014.jpg (286.61 KiB) 46 mal betrachtet

Gymnopilus junonius_20cm Hutdurchmesser Stiel 45 mm dick.jpg

Were your finds growing on wood?
To me, they look like they’re growing on soil???
Did you smell them? To me, they look like very young Tricholoma sulphureum.

https://www.alamy.com/fungi-sulphur-kni ... 81526.html
https://123pilzsuche.de/daten/details/T ... ureum3.jpg

[BubikolRamios]

Smell not my strong side. OP image on ground.
Also landed at T. sulphurium as alternative. See this, fat stem at bottom also mentioned as option al local. desc. for T. Sulphurium, And no white base mentioned at local desc. for T. Sulphurium.

[abeja]

I've never seen them this brown ...
But there is a variety, T. sulphureum var. bufonium, that has a brownish-purple cap, which - when dried out (?) - might possibly look like this, but actually still has yellow gills ...
For this species (or variety), some sources (123Pilze) describe a stem that’s thickened at the base (like a club) and lighter in color toward the base.

Are the brown one supposed to be the same species as the little yellow mushroom??? I doubt this, the gills are getting reddish-brown spots.
Maybe some other Tricholoma ... one of the brown ones (Tricholoma ustale ... or similar).
EDIT (several times):
And what about the gill attachment? That doesn't really fit Tricholoma (the brown mushrooms).
I'd try making a spore print to see what color the spores actually are!
Maybe it's “just” Gymnopilus penetrans, though I remember it being a bit more colorful.

PS:
The smell of T. sulphureum is nauseating - (for me) like burnt horn, but with a distinctly sweet, floral note alongside it (or “behind” it?). Some people barely notice the repulsive smell; they only perceive the “sweetness.”