clownfish keep dying one always lives

[halo2rain]

Ok so im new to the hobby first time on this forum posting. Been reading it for about a year before I got the tank (I do ALOT of research before I get into something like this) but let me get into my problem and its not a mantis shrimp I always find the bodies and take them out

Hi guys my aquariums is as follows (sorry if my spelling is wrong on anything)
75gallon set up for about 2 months now
about 80+/- lbs live rock
60lbs live sand
fluval 405 canister filter
seaclone 100g skimmer*
temp 78-80 bad heater need a new one (temp fluctuation is not bad it just creeps up and down over a week or so never above or below those two though
48" odyssea t5ho lights 2 10k 2 actinic

Params
1.021 sg*
0 amonia
0 nitrites
5-10 nitrates
15g water change every 2 weeks
fish list
1 snowflake occelaris 2" +/-
1 lawnmower blennie
1 neon dottyback
1 six-line wrasse
1 diamond watchman goby (sits at bottom eats sand all day) lfs said thats what it was but heard theres two different ones that look like that
1 neon goby

inverts
1 skunk cleaner shrimp
assortment of turbo astreous and 2 other kinds of snails
I think they are blue legged hermit crabs maybe 10 to 20 they come in as hitch hikers I bout maybe 5 and they either hitchhiked or made behbehs lol
and one 2" bubbletip anemone its been in there for about 3 weeks now originally got it for the clowns but then it moved to the very back of the tank where I didnt want it like they tend to do so I hear lol

anyways my problem is ive had the tank running for about 2 months now since may 26 2014
I started out with 2 clowns after the tank got done cycleing the first time no fish just a table shrimp in it for a week then out one clown died due to second cycle is what lfs told me I added 2 domino damsels and the neon dottyback 1 damsel died in first 24h second damsel died 1w later added lawnmower blennie and sixline wrasse 6 line jumped out and died 2 days after I got it cause I forgot to put lid back on added another one and the diamond watchman goby added another clown it lived about a week and was doing fine then died added another clown it died added another clown it died*
went to one of my buddies hes been doing marine for about 12 yrs he told me that my clown might just be really aggressive and killing my other clowns so he told me hed give me store credit if I bought a pair of clowns from his tank so I did that I get them put them in my tank 4 days later one of them kicked the bucket now im back to having just one clown again and all other fish are still alive

But here is clown types all occelaris that have died
1 false percula
1 misbar false percula
1 extreme misbar false percula (almost a naked clown only had a tiny bit of a white spot on its gill maybe a 1/4" wasnt ick either lol
1 snowflake clown

im sorry this is so long but I really want a clownfish couple dont care if they breed just want a pair of them and a anemone for them I know clown/anemone hosting takes time but I think its cool to watch*

also acclimation procedures ive tried have been*
Float and drip then transfer fish only
float and drip then pour bucket into tank
float then transfer
Float then pour bag into tank*

what im trying to figure out is why only one of my clowns dies even when I put them in as a pair and the other one doesnt is there anything I can do that im not doing to prevent this or am I doing this properly and its just the fish being weak and stressed to badly to the point of deathand sorry if this should be put somewhere else I couldnt find a clown only section so I figured itd go good here lol

 

[halo2rain]

So the fish that are living right now are1 snowflake occelaris 2" +/-
1 lawnmower blennie
1 neon dottyback
1 six-line wrasse
1 diamond watchman goby (sits at bottom eats sand all day) lfs said thats what it was but heard theres two different ones that look like that
1 neon goby

The 4 clowns that I mentioned are the ones that have died. I took the one original clownfish to the pet store and had it traded for the pair of snowflakes one of the snowflakes has since died*
the 2 clownfish that I had originally i could tell them apart cause the lines are different on them and from the point of the first clownfish dieing I got dfferent looking ones the colors were way different so I could tell them apart
but I checked the water parameters before adding fish its always at 0 for amonia and nitrites my nitrates are usually at 5-10 if a fish dies I havent gone out and just bought another fish and plopped it in that same day its usually been days inbetween and I have been checking my params about once a day if not twice a day since the one died nothing ever changes I have taken my water to 3 lfs one my wife works at and 1 where my buddy works at all are always the same 0 am and 0 nitrites 5-10 nitrates so its not the parameters sg has been checked with 2 different refractometers and 3 different swing arms tell me if you need any more info on my tank parameters