newbie question re dead bees in nuc

[fullframe45]

This will be my first full year with the bees so im afraid i am lacking in knowledge so maybe someone can help answer a question for me.
Last week i did a quick inspection of my nuc. Paynes poly adapted to take 8 frames,on inspection and i may add it was a beautifully sunny day and around 18 deg.
The nuc was busy with lots of bees flying in and out and bringing in lots of pollen yellow. Inside i found 2 frames of capped brood patchy not full on frame.lots of pollen and nectar ,some lava and some eggs,ddi not look for the queen. 3 frames of partially covered honey and two old black mouldy frames on outside and a dummy board.
Now this is where i think i have made a mistake.I took out the 2 mouldy frames and replaced with new foundation. The bees were very calm all through inspecting and i came away very pleased even though i think this is a very small colony.
I visited today and saw small clusters of bees maybee 30 in total on the landing board dead .I did not open up as it is very cold here today and im concerened if i have contributed to this by removing the old frames and maybee taking away insulation.
Hopeful i can have a look at the weekend as the weather looks better.

 

[jenkinsbrynmair]

Bees turf out their dead daily, if it's a wee bit cold they just dump them outside rather than carrying them away.
At this time of the year you start seeing the old 'winter bees' finally shuffle off this mortal coil as the strain of rearing new and increasing brood gets too much for them.
Personally I would have left it a little bit longer before swapping comb for foundation, but I doubt much harm done.

 

[fullframe45]

Thanks for reply,with them only being small in numbers every one counts .Hopefully the weather will improve for them and us. Thanks again.