BLUE TONGUE SKINKS

Hello, I recently (a little more than a month ago) got a 4 years old Merauke named Po, it is the first time I own a BTS. I am a bit worried because Po has been behaving weirdly recently. Ever since I got him, I would feed him twice a week because he is really huge, and he would eat everytime I fed him until his dish was completely cleaned from any trace of food. I feed him dog food with calcium and vitamins supplements and fresh fruits, (like bananas), and recently, he started to eat way less. He only touches his bananas and one or two bites of dog food, and then leaves. He often even waits for me to feed him in front of his enclosure's door because he's hungry and when I actually give him food, he barely eats it.

I have a few ideas of what may be happening (after doing some research) but I really need someone experienced to help me decide what to do.

1. The temperature of the enclosure is too low: This winter, the temperature of the enclosure was wonderful, and he was eating a lot, but now that it's the summer and it got hotter, I noticed that because of the AC, the temperature has gone down a little. It's currently around 100 in his basking spot, and it used to be around 110. The thing is that he doesn't seem to be cold at all because he switches between his hot and cold hide all the time like a normal skink would.

2. The type of food is different: I recently changed the type of dog food he's eating. (It's the same product but in a different flavor.) I wanted to give him a bit more variety, but he may be a very picky skink.

3. Weird sickness or something??? : I noticed that, recently, he keeps missing his food when he tries to eat it... Like, he keeps taking a bite of his ceramic dish instead of a bite of his food, and he didn't do that before. It's like his senses are affected or something, idk. He didn't do that at all before, and honestly, I used to be quite impressed by his eating skills, but now they're just miserable and sometimes I have to present his food in a spoon for him to find it. (i must sound absolutely crazy, but I'm really worried)

So, yeah, I don't know what to do? Should I feed him less? Should I adjust the temperatures of his enclosure? Should I go to the vet?? ((( or maybe I'm just worrying too much... I recently lost a snake, it wasn't my fault, but it makes me worried about all the care that I give to all my animals... so yeah, I'm probably going crazy )))

HELP!!

Well, mine snap at the air and bite their dishes too. That's not a worry. Your temps seem fine. Four year olds really do not eat as much as four month olds. The older they get, the less they eat. My males especially. Sometimes they'll gouge themselves and not eat for another week. They pretty much just pick. Bi-weekly feedings should suffice, and should he get hungry, I always leave some dry food in there at all times. How about showing us what he looks like?
Adding some hard boiled egg to his food when he gets picky should wake up his feeding response!