6 Month Old Baby Dragon only eating every five or so days.

I have two baby bearded dragons roughly 6 months old, and Ive noticed within the last three weeks (since the cold weather has set in) one of them only eats a cricket and maybe some vege every five or so days! The other is a big boy and eats four every second day, they've never been big eaters, and the smaller one, we think is female as theres a dramatic size difference and overall look, is the one who doesnt eat often or much at all. Ive tried woodys but they're not fond of those and they wont take mealworms, we have a heat lamp on of a night and they both become active when its on, and we have the UVB on of a day with the heat rock on. The smaller one in question also likes to dig holes and lay under the water bowl and heat rock too, when it gets to cold.

I just want to know if anyone can tell me what might be going on with our smaller one? Ive asked the pet shop that sold them to us and they said its fine, Im just super worried.

Thank you!

How big is the enclosure? What substrate do you use? When is the last time she had a bowel movement? Also using a heat rock can be very dangerous for the beardie. They have been notorious for burning them. What temp is your cool side/warm side? How long do you keep on the lights? Is there water available? if so do they drink or lay in it? If not do you mist or soak them? If so how often?

basking spot temperature ?
warm zone daytime temperature ?
cool zone daytime temperature ?
overnight temperatures in tank ?

photoperiod (when are lights and heat turned on) ?

substrate ? -- you mention digging - remove that substrate and use either loose floor tiles or paper towels or paper sheets for the substrate (this will reduce impaction risks to near zero) and give a dramatic improvement in tank hygiene too.

what is used for a basking globe (photo) (VERY IMPORTANT) ?
what is the UV globe/tube ?
>>> how far is it from the basking spot ?
>>> what is it's brand (VERY IMPORTANT) ?
>>> what is it's wattage (VERY IMPORTANT) ?
>>> what is it's UVB rating (%UVB) (VERY IMPORTANT) ?
>>> under or ontop mesh lid (VERY IMPORTANT) ?
Guide for setting up temperature and UV : viewtopic.php?f=34&t=235611

body weights of dragons ?
size of crickets ?

how long since last poo ? impaction from ingest substrate has made many bearded dragons very sick and even kills them on a regular basis - especially stuff like wood chips, bark chips, kitty litter, seeds, husks, sand, peddles especially calcisand / vitasand (this stuff is lethal to bearded dragons).

Sharing tank is going to be the main issue, even if you think they are inseparable and love each other, I can guarantee one is getting the lions' share of the food, the best basking spot, the best napping spot and one will be thriving while the other will not be. It's only a matter of time before the domination / territorial behaviors become violent and very bloody - the dominant can easily bite off a leg or tail or even kill the submissive.
The smaller dominated juvenile is terrified and trying to hide from it's larger very aggressive dominant tank mate.
It's not eating because it dares not eat when the larger juvenile is watching it , even if an insect comes close enough to eat.

THE TWO MUST BE SEPARATED IMMEDIATELY and housed in their own individual tanks and must not be able to see each other except very occasionally and MUST NEVER BE ALLOWED TO PHYSICALLY MEET.
A cheap way of housing two juveniles until you can build or buy their individual forever homes (4x2x2 tanks) is to use 100L - 150L plastic tubs, these can be stacked and are very easy to convert to very good temporary lizard enclosures. This is how I set up my two 100L rearing tubs : viewtopic.php?f=34&t=233480

I'd move the larger juvenile when you have the second tank or rearing tub ready , it wont harm it to go through a period of relocation stress , where a relocation into an new tank will be very hard on the already weakened and highly permanently stressed smaller juvenile , so let the little one keep the tank it's in and improve the lighting , and setup for it to give it the best chance of recovering .
Don't be surprised if the little one makes dramatic improvement once it knows the larger juvenile "has left" and it starts to feel happier and more secure and less stressed.

Other animals / pets scaring it ?

Remove the power cable to the heatrock -- those things are bad news , many a skink and dragon and gecko has received serious tummy, chest, tail and leg burns from these , they are prone to failure and overheating.

Also 5 month old juveniles are far from adult and have at least 18 months of growth potential in them. A feed of insects every second day is totally inadequate for a 5 month old , they should be housed separately, fed live insects twice per day and offered salad AS A SUPPLIMENT , less will result in malnourished dragons who are not growing/developing properly.
At 12 months old it's one feed of insects everyday + salad.