somelinkias do take to spot feeding, however, they still die quickly because you are not providing them with the proper nutrients. it is still unknown what linkias eat, thought it is believed to be on live rock. This is why a minimume of 100 pounds of live rock is required to be able to keep this species.
Take it back to your LFS. In my opinion, although they are beautiful, they are not suitible for most home aquariums.
your levels should be perfect. your tank should be established andmature, you need tons of live rock, perfect qater chemistry, and a salinity of 1.025-1.026