This might seem a bit log winded but I feel that background info may help me get the answer or suggestions I need.
Age CB May 2012 bought him end of june 2012. Housed in a small tub and was a good feeder on rats of appropriate size. When grown on he was moved to a 3ft x 13" x 18" vivarium heated with a cermamic bulb on a thermostat, cool end 27-28c, warm end 30c and basking spot 33c. He continued to feed regularly.
Then in June last year we moved him to a 3ft x 2ft x 2ft vivarium and created the same temperatures as peviously stated using the same equipment. We added extra plants, a larger water bowl and other decoration so the vivarium was not big and open. He was very active climbing around and he continued to eat for a few weeks but then feeding started to become erratic.
He then stopped eating in december 2013 and has not eaten since. Weight was holding steady at 1.2kg but has now started to drop weight at a rate of 16g every 14 days roughly. Seems ok in himself active, bright eyed and no wheezing and is still over 1kg at the moment. We have continued to offer rats at a rate of once every 2-3 weeks and have tried varying sizes to try and entice him. Have tried rats heated as that's how he use to eat and even tried not heating them.
I am wondering if this is just breeding season fasting or is this related back to the move to the larger vivarium when his feeding became erratic after a few weeks? I am not panicking YET as I know they can fast for a long period at a time, its the fact that weight is starting drop quickly.
Should I just wait and see or do you think this is linked to the move?
Should I put him in smaller housing? Maybe a tub? I have tried the theory of changing and disinfecting every thing in his vivarium so he thinks its new but no luck there.

Thanks for any advice or suggestions you can give me.