Thank you for replying so quickly!

How old is he? - nearly 5 months
How big is he...from the tip of the to vent ( his bum) - 2 inches
Is the 'puffy' anywhere else on his body? - No just this 1 place
Most importantly---does this ever disappear ? - not sure what you mean, if you mean the puffiness then this is the first time i've seen it. Never seen it on my other one Toby, but then again Toby never makes a sound.
Have you heard him call? - yes. Calls at different intervals through the night and verrrrrry loudly for about 10 seconds

(both my frogs are too young to sex so i just gave them names i liked, i don't know 100% if Penelope is a boy or girl but i'm guessing boy since i've read everywhere that mainly it's the boys who croak so might have to switch Toby and Penelope's names around )

Sorry about the bad quality photo, was trying not to disturb him/her too much by turning my lights on or anything, here's another one 2 took last night (sorry about the darkenss, doesnt hep that she was brown at the time) http://i.imgur.com/c3tcMH4.jpg http://i.imgur.com/yx2RUPV.jpg my froggies are sleeping at the moment and they sleep all squashed up behind my foam background (the one you get with exoterra terrariums) so it's hard to get another picture until they wake up.

I couldn't tell any redness at all and Penelope was just jumping around her home as usual. She was a little more energetic than she usually is at that time but apart from that there's been no behavioural changes. Both of my frogs change from being a bright green colour to a dark brown as well


What are the temps and humidity in the enclosure? - Temperature is always 25°C give or take 1 or 2° and their humidity i try and keep between the 40 and 50 mark on the little stick on exoterra hydrometer
What are you treating their water with - Their water is treat with Aquatize conditioner (1 or 2 drops per L of water) and it's changed every day

I've been doing some research about what it could be and some websites say it could be irritation from calling so much? Not sure if this could be the case but it would make sense considering Penelope is so small but his/her calls are very loud