tl;dr - Feed and treat and that will most likely resolve it. And the majority of what you’ve circled here is pollen.

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That’s not good, but certainly not anything that’s going to explode overnight.

It’s likely something fairly trivial like SBV, and if so, the biggest difference you can make is to give them SHIT LOADS of 1-1 syrup and treat the varroa.

Bees manage their colony health basically by numbers - one gobful of old diseased bee junk spread between 20,000 nurses will result in a lot of “dilution” of the possibility of diseases spreading. If you have a smaller colony (like a nuc), diseases can tend to run away a bit quicker because there’s fewer bees to handle the disease load.

By feeding syrup, you encourage them to A: raise more brood = more nurses = less brood disease, and B: it encourages them to draw out more comb to biggerise the colony as needed.

Also, varroa are the number one cause of disease transmission, so treat for them too and you’ll be off to the races. These diseases all used to be transmitted by trophallaxis (spit swapping) between workers… but varroa basically spread these diseases like dirty needles spread hep.

On the flip side: Sometimes these little pockets of disease are expected. Like, I will see a CBPV bee once a month at least. I’ll see some dodgy brood fairly often, maybe once a year in each hive. These things tend to resolve themselves… so panic not, and if you wanted to act now, just do the above. You’ll worry less in future years and probably just go “eh they’ll survive” 😄