Your axolotl does look quite poorly.
He looks as if he has fungus on his gills.
In the first and second pictures I can see a white spot on his head, between his gills, but I don't know what it is. Perhaps one of the more experienced keepers will be able to give you more advice.
How long has it been since he has eaten?
It is very important to test the water. It might be worth ordering something like the API freshwater master test kit online, I find Amazon, etc. a bit cheaper than in the stores, and you can get next day delivery.
For fungus you could do a bath with tap water (do not use dechlorinator), or do a salt water bath. Tap water is said to be less irritating than salt water.
http://www.caudata.org/forum/f46-be...axolotl/72698-salt-bath-picture-tutorial.html
However, I do not know what the spots are, and we do not know if there is a problem with the tank water. I would certainly keep him out of the main tank and in a conatainer of clean dechlorinated water. Do 100% water changes daily on the container.
Also have a very close look at your other axolotl to make sure that one does not have any signs of fungus or anything else. If in doubt put the other one in a seperate container of dechlorinated water.
Fridging is usually for constpation/impaction, or as a last resort for other major problems, to slow the metabolism down. Just make sure that the fridge is not too cold.
http://www.caudata.org/forum/f46-be...ick-axolotl/85263-axolotl-fridging-guide.html
As it is summer, and your little one is unwell, it might not be a bad idea to keep him in the fridge until you can get some more detailed advice from the more experienced keepers.
I'm sorry I can't identify the spots for you. I'm still relatively new to this and have had my gang for around 6 months too. I don't want to give you the wrong advice and make the situation worse.
If you do keep him in the fridge, make sure that any water changes etc. are with water that is the same temperature, as fluctuations in temperature will cause more stress.
Please keep us posted and I hope the others will be offering advice soon too.