i see, what do you do with baby chams that are not eating well? where do you put them? big cage or small cage? thanks!
Generally I do not have this problem. When I do, I simply isolate the baby into it's own cage which is the same size as the other cages I use for babies.
I keep them in small groups and start them in 22 or 38 gallon reptariums nowadays which I orient long side horizontal, which keeps the floor walls and ceiling near the babies so they always have easy access to insects (which I offer loose in the terrariums until the babies are a little larger and able to eat a little larger insect and a little smarter about going to a food dish- just personal preference- I've started them feeding out in bowls as hatchlings as well, but this is my preference so less dominant individuals don't have to brave the march past more dominant individuals to the bowl). But in the past I've used lots of different containers successfully including plastic tubs similar to yours, 30 gallon aquarium tanks, etc.
I just consider size a balancing act of thermoregulation vs feeding requirements. Smaller = more difficult to set up proper thermal variation in the environment, while larger = more difficulty for a baby to catch food.
If a chameleon is alone and not feeding well, the first thing I check is the environment. Can it get as warm as it wants? Can it avoid the heat and is there enough temperature variance for true thermoregulatory behavior (not just a "hot spot" and cool every where else- there should be a true range so the chameleon can select the exact temperature it wants at any given moment). Is there enough light (won't feed in low light situations such as at the bottom of a tall enclosure away from the lights- sounds like you are doing fine with this)? Is the animal drinking? Is it getting enough calcium/d3 and multivitamin (More a consideration if the animal is sleeping or keeping eyes closed- sounds like you are doing fine with this as well). Is he getting enough water, and not too much ( for a baby veiled- a light misting to haze the sides of your tub and a spritz or two directly on the cham 2x per day along with a drip cup is plenty, or a light misting a few times a day is still OK at this size as well- but make sure the enclosure dries out completely between mistings. These are the kinds of things I look at.
But for you- I'd say a couple of things could help-
First- thermal variation with a heat lamp.
Second- Sometimes it takes them a few days to settle in. Just offer food, and water, and don't touch or mess with him any more than absolutely necessary. This might be your only real problem in this case. It could just be that he's only been with you less than a week and needs a little time to settle in. You haven't mentioned if you occasionally handle him or reach into his enclosure and move things around - but anything like that will result in a shy individual taking longer than usual to settle in and start to feel safe and feed well. Time and a hands off approach might be the only real obstacle here.
Also- mealworms- I would wait until he is feeding well on crickets before introducing mealworms again. I personally offer baby mealworms right off the bat to my hatchlings alongside baby crickets, baby roaches, fruit flies, etc- anything small enough is fine. But- because he is showing some reluctance to feed and because crickets are more well rounded nutritionally and a bit easier to digest- I'd wait on yours until he's eating crickets well on a regular basis.