The bright red vein in the tail could be one of two things. If your fish is light colored and has always had it, that means you can just see it better due to his genetic makeup. The other thing I would guess is that your tank had a minicycle and the nitrite levels might have elevated, then settled down before you tested the water. Doing a water change might help put things to rights if that's your problem. Now the white specks; that could be anything, but to me it sounds like ich or a fungal infection to me. If they look fuzzy, that's a sure sign. I'm guessing it's ich because Pimafix is effective against fungal infections and both internal and external bacterial infections, and you say you had no result. I don't know for certain, but I would suggest using salt, not medication. Dose the tank with 3 tablespoons of salt pre-disolved in 1/4 tank water for every 10 gallons. This should get rid of whatever the problem is unless it has to do with water quality.

I wouldn't separate him, if he's acting healthy, there's nothing to be afraid of I would treat the whole tank with a little salt though, unless it's so big that it'd be a waste. If you'd rather save the salt, go for a big water change and some thorough gravel vacuuming instead, that helps a lot

Good advice.  I don't think a cup or my hands would work, given the depth of our tank.  If I tried that I'd probably need a snorkel and end up catching the fish in my teeth.
In any case, we did a water change and gravel vacuum.  Izzy is still happy, healthy, and hungry, so I will stop worrying for now.