Experience calculation

[OldTrees1]

Is this 1 encounter or 3? A bit of both. They didn't get any break time inbetween but neither did the enemies get to gang up on them. You could treat it either way depends on if you wanted to be easier or harder. I would treat them as separate encounters but increase the CR of each encounter slightly to symbolize the added challenge.

I would not boost xp to compensate for no loot. Eventually you would have the PCs be under equipped for otherwise reasonable encounters. Rather I would just remember to add a bit more loot next time.

Yes you a right that things that modify the difficulty of an encounter also modify the xp gains(as I referred to above when I would bump the CRs up a bit).


In conclusion:
You had 3 waves(3 encounters) made up of a CR 1/3, a CR 1/2 and a CR 1. However the CR 1 was nerfed to 15ft speed so let's call it a CR 1/2. Then let's increase the CRs a step as a best estimate for the lack of break time between waves. So not we have 3 encounters of CR 1/2, CR 1, and CR 1. Since this party was at half strength(only 2 members) that sounds about right given your description of the PCs' struggle.

Now XP is given on a Monster by Monster and Player by Player basis according to table 2-6(pg 38) of the DMG. So you have 2 1st level PCs. The first gets (150xp(Level 1:CR1/2)+300xp(Level 1:CR1)+300xp(Level 1:CR1))/2(number of players) so that is 750/2=375xp. There is an example at the top of the 2nd column on page 37 that gives more detail of stranger cases(like PCs of different levels).

When there are multiple monsters in an encounter I houserule the XP is given Encounter by Encounter to reduce the work. It works rather well.

Edit: oops I missed that there were 3 kobolds.