Question: Possible fungal...?

Hey everyone,
I know there are a hundred threads on fungus infections here, but I haven't found anything quite like what has started affecting my Phree...
I've attached photos of his (What to me seem to be) normal spots (left hand side), and the right hand ones which have in the past two days started to change slightly... Compounding it is the base I've had to put down on their summer tank (Coral sand-gets EVERYWHERE and seems more dusty than anything I've ever used before -So much for the dust free tank bottom promised by
the packaging..:nono
Water parameters...Aren't the best...
Temp is currently hovering around the 22c mark (Though dipping down to 20c with a nice water bottle)
Others...I'm not too sure of as I'm still saving up for a testing kit, however, the tank's running a well established filter sponge, an airstone, and a heat sink chiller which seems to be also getting most of the excess waste as well.
Many thanks in advance!

As far as i can see on the pictures those are heatspots.(dont know how to exactly call it in english)
But your axolotl is getting it cause of the warm temp in his tank.
So cool down the tank and it will fade away slightly i hope but keep an eye on it cause it can be a fungus. Like i said 'as far as i can see' ^^

*Exhales* Thanks so much for that...Only problem now is getting the temp down another notch...I'm already bottling, heat sinking, and got them in one of the coolest rooms in the house (Oh the joys of the Australian summer...)
Once again, Thank you so much for putting me at ease (And I'll definitely be monitoring religiously)

how are the water parameters not the best? If you have ammonia/nitrite in the tank I'd do my best to remove it.

More in terms of the temp being rather high, and I'm not entirely sure of the ammonia levels (No smell, so I think i'm okay), and not to mention the tank they're currently in is only 20L (Before people start screaming about injustice, it's over a foot, they're at 15, 13, and 11 cm, they've got room to swim freely and their big 4 ft tank is currently climbing towards 29c (Which the guppy colony that is currently keeping the biomedia alive is absolutely adoring)) and therefore more likely to have a major spike than the four footer...
And yes, I have been keeping an eye on water changes (though I've been losing SO much to evaporation on both tanks-fifteen litres from the big one in just over a week..., So I've been primarily siphoning off what I can then topping up three times as much (Had a MASSIVE scare a week ago when the tank ran out of water... Very uncool...)