yea 10 for a new 55 gallon was too much - 5 dying was nature's way of telling you this - keep it at the remaining 5 for the next 3-4 weeks and then, ONLY after your tank is cured of the ick, slowly add 2 fish at a time in 2 week intervals so that your beneficial bacteria can stay in tune with the added bio-load.
which fish are they?
btw, the salt will also slow down the nitrogen cycle so at this point you want to focus on getting rid of the ick with the least amount of deaths but this will be tricky - your tank started off badly but don't be discouraged as in a matter of time, it will work itself out. take it as a learning experience and go from here.
whether you choose the salt method or the medication method (i'm partial to AP pros's Quick Cure product
http://www.aq-products.com/APpro/quickcure.htm)
be sure to up the temp to about 83F (I've even upped it to 85F when I dealt with my ick) but increase the aeration of the tank greatly using a strong air pump and a large bubble wand/strip to compensate for this as that high a temp reduces the oxygen level in the water. The high temp speeds up the lifecycle of the Ick and so the meds can kill the disease at its earliest stages to prevent reproduction. Follow the directions on the label of the bottle exactly.
In terms of a water conditioner, I highly recommend using Prime by seachem
http://www.seachem.com/products/prod...ges/Prime.html
It's all I use. Good luck and please keep us updated.