It's a nice looking viv, you would expect no problems with it I'd imagine. Ok so he has hot and cold spots with hides at each end in effect which is good so that clears that.
I use shop bought raspberries and I give them a really good swill and he hasn't had problems, only a couple and sliced up small as they have a high water content which will give it a bad stomache (runny poo.)
2 more poos in the last hour tho.... That's making it clearer. I'm in no way a specialist but what I would guess would be that it's approximately a year old or slightly younger, some grow slower than others.
It's gone a lighter colour because its about to shed, a warm bath every other day should help it a lot.
I think.... The reason its been basking all day is because it needs the warmth to digest and what its trying to digest is Substrate. That would explain why it's basking all the time and also why it's pooing a lot now. Is unblocking itself. Try the impaction routine (bath and belly rub) hopefully then after a few days it'll be back to it's cricket crunching days.
I would also recommend either feeding it in a separate enclosure or hand feed it. That way it won't ingest the substrate, what is it on at the moment, calci sand did you say? A lot of people wouldnt use that for this very reason, I use wood chips as they're a lot bigger there's lessor a risk if it eating it, though it happens now and again.
As long as its got somewhere to hide away from the brightness and it's guts are all flushed out then I personally can't see there being any other problems. Also reptiles can sometimes be a little strange when you first get them, getting used to new surroundings etc. And it's also a lot harder to care for babies than juveniles or adults.
See if that works, I have faith that it will.
If its still worrying you in the best part of a week then well have another think
All the best