you and i are not really on the same page, with the same ideas and goals, so applying some of what i said in other posts, mixed with my reply to your recent post, doesn't necessarily work 
i am here on the forum (and i am a newcomer here) to talk about our experiences at Pro Exotics with our Ornates and going (basically) against most accepted Uro husbandry, which i feel is dated and detrimental to the animals, while we are basing our husbandry on our experience and success with other lizards.
getting to...
simply covering your screen top to limit ventilation is not necessarily a good idea unless you are pursuing a wider, grander change in husbandry, so maybe follow up with my posts of the last few months to get an idea of our direction, because it may not be for you.
in reply to your first post, i asked for more details not necessarily because i can help, but rather because anyone that wants to address such a problem (and extremely common request on this forum, and many others) should get as much info as possible before reasoning out scenarios and possible solutions. there is much too much quick answer type replies here that fail to take into account the unspoken variables that are important in forming an "internet suggestion".
boy, this is wordy 
anorexia simply refers to lack of appetite and reluctance to feed. i think that is your animal's problem, not "brumation".
and i know nothing of captive "brumation", we don't cool our monitors down for winter, and we aren't cooling our Uros either. i have learned with other lizards that it is simply not necessary (when part of an appropriate overall strategy).
but anyway, your temps are high, you continue to offer food, where is the brumation? i think the problem is more likely related to parasites (strong possibility) and setup.
if you are going to cool (brumate) for the winter, which we do with colubrids, then you stop feeding and go COOL. temps and lights and feedings are not here and there, every three days, kinda thing. you just go down, and stay there until it is time to come up.
however, with a new animal, especially one of questionable health and background (put money on that animal being wild caught), there needs to be a health and stability evaluation to determine if the animal is strong enough to go down in the first place.
start with a fecal, for sure, it is an inexpensive look into the insides of your Uro. if you come up with bugs, then clear the mind of brumation and instead concentrate on a worming cycle, and getting a good feeding response and weight on the animal.
if the animal indeed comes up clean from the fecal, then still consider weight. if a kingsnake has a poor feeding response, and is underweight, we will hold it out of the cooling cycle, so that it can continue to feed and gain strength and health.
to address your last three questions from this thread...
substrate- we have been talking about this for the last three months
we use a diggable, burrowable soil substrate for our lizards, that is the short of it. there are probably 5000 other words i have already written about it that i can't re-cover here, that is why i suggest scrolling down, and looking at the recent archives. tough, and subtle subject, i can't rehash it in one post, sorry 
night heat- there should be some, but how much? substrate changes or no, i think 70 and above is best for the Uros. you can use heat pads, heat tape, red bulbs, ceramic bulbs, heat panels, lots of different things for night heat, it just depends on preference and setup. we use room heat because we have an entire facility 
age- i have no idea, sorry.
best of luck to you and your animals!
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robyn@proexotics.com
Pro Exotics Reptiles