Context
Today I changed Luna's water 100%. His natural curiosity got him into the cup no problem (though he did get fussy once he figured out what I was doing) and the whole procedure went by pretty smoothly.
Luna currently lives in a one gallon desktop aquarium (getting a 5 gallon in the mail soon

). I buy his water from a local pet store as a way to support a little mom-pop type operation. The water they sell has been great, so I'm not worried.
HOWEVER
My room mate used half of my gallon earlier in the week and forgot to replace it. The mom-pop pet store wasn't open, so I purchased the rest of the gallon for a couple of dimes at the local petco.
Question
Luna seems to be OK, but he also seems a bit overwhelmed by the whole ordeal. He moves rather slowly at the moment, breaking out into sudden, skittish outbursts. Is this all a reaction to his water being changed, or is there something up with the water I bought him? I've been forgoing the purchase of a water testing kit until the 5 gallon arrives, can his water be tested for quality or does the kit only cover ammonia and nitrites?
I think maybe I'm just paranoid, but still...