Red Leg? I hope no ):

[Bolisnide]

What are symtoms to be looking out for? He ate 6 Crickets just an hour ago, and is still active.

A good appetite is always a very promising sign, so that's very good.
I would have no idea what so ever if it is red-leg, or some other type of infection. An examination by a vet is the only way to know for sure. Any sort of red or black mark or lesion, would immediately concern me. Make sure his environment is very clean, change out the water dish daily, wash the water dish in HOT water, with a clean paper towel, dry with a clean paper towel.... I assume you already know to treat the water with a conditioner, or use 100% spring water.
I suppose a very thin layer of NON-PAIN RELIVER neosporin can't hurt while you're finding a vet.
I would advise the vet visit immediately. Infections can proliferate very quickly, then it would be too late.

[flybyferns]

Hi 1Dumpy ,
Bolisnide has got you well covered !

It would be great if you could still post some photos , however.
Photos always help. Photo - try to get as close to this spot as possible !

Hopefully you will be able to follow her excellent advice as soon as possible.

Lynn