Is this Dry Rot ?

[FortnamsTea]

Victorian stone-built end terrace. Want to sell. In Scotland so had to commission Home Report.This revealed rot in exposed timber in basement ceiling (under hallway floor). Grade '3' (immediate repair) for both rot & floors on HR. EA said 'market & sell'. Because I didn't want to have problems down the line with a sale (& it seemed 'dishonest' now I know there's a problem) I've exposed more ceiling & it's across a few end joists. It doesn't look recent. It doesn't smell (at all). I've booked a specialist in rot, but while I wait (2 wks) can anyone advise? (appreciate not a 'diagnosis')
Pics attached hopefully

[Images removed by MNHQ at OP' request]

On Facebook post this on the Your Old Home conservation and repair UK group. You will get very good advice from this.

@Tortephant Thank you. I am not on Facebook so I'd have to join.

OK, call the SPAB helpline and they will advise.

Be careful of any one that is selling you something is my big message here.

@Tortephant Good advice, thank you! Not trying to be difficult, can join Facebook & will look for group.

@Tortephant I did as you suggested & it has been helpful thank you.
I will ask MNHQ to remove my pics now in case it can be linked across.

Pretty definitely dry rot.
And evidence of woodworm.
Some of the joists may be salvageable by cutting off rotten ends and splicing in new wood whilst adding a membrane barrier at the ends.
Treatment with chemicals or borax solution will prevent reoccurrence.
That is disruptive though.
But it also looks like the floorboards are suffering a lot.
Suspect the whole floor will have to be taken up and all joists and boarding replaced and air bricks opened up or in installed to ensure ventilation is correct.
That will be very disruptive.
See what the professional says.
Sorry for the bad news.