How is this happening ?

Even if you moved it with sand still in it, the movement in transporting it is enough to stir up the sand bed resulting in toxins being released. Add that to a nano sized tank with fluctuating parameters.
In my nanos I've only been able to keep these mollies and the mandarin. The damsels and clowns died. I believe it's from the swings of ph and salinity increases from evaporation.

Sent from my HTC6525LVW using proboards

How long have you had each clownfish before it died?

Ph swing at night is very small and doesn't normally cause these kind of problems does it? My ph only changes about 0.05 at night time and was effected very little when the landscaping pistol shrimp was moving sand in my tank nightly and never slowed down.
I just think once again if they lost clowns before the move with the tank already cycled Idk how this could be the sole problem? How many people out there successfully keep clowns in a nano? My guess would be allot since it's one of the most popular fish in this hobby.

Two weeks or so? Sounds to me like it's one of two things going on. Either something in your tank is off and causing a toxicity to fish only or it was most likely poor quality fish to begin with. Probably mishandled, under fed or diseased from the wholesaler. Many times we can buy fish that have internal damage from mishandling or internal parasites that we cannot see. I've had it happen many times. Bring a fish home and it will be fine for a few days to a few weeks and then either all of a sudden it will die or it will slowly start to get skinny and wither away. How fish are collected, transported and handled during a sale makes a huge difference In the fishes survivability in a boxed enclosure.

Yea I've noticed a bunch of his clowns were kinda crappy looking the last few times I've been there. That's not saying easy aquariums is to blame though. Like I said it's a supply issue. The upside to ordering from a source like LiveAquaria is that if the fish dies before the 14th day is over you get to report the loss and get refunded the purchase price. No local store can do that. The $34.99 flat rate overnight shipping really isn't that bad when you consider the fuel cost to drive to most local fish stores unless you live within spitting distance and only buy cheap fish. You said your water parameters looked good? What were they? Are you using an activated carbon, filter media or poly filter to remove any possible unseen chemicals or toxins that could be in your water?

I have blastos, hammers, frogspawn, zoas, mushrooms, a anemone that's hated me since I got it (It survived the tank cycle). I think that's it. I have some Xenia too. All look amazing. My parameters are all zero other than nitrates which I've struggled with since I got it. I top off all the time and last time I did a large water change it was with Easy's water

My nirates stay around 20ppm. Which is totally fine for fish, and my coral seem fine by it too. I use the crushed coral bottom, so I've heard that could be the source behind those.