I know if my leathers are not doing so great I will do an Iodine dip for them. Just get a bowl or milk jug and cut the top off and fill it with tank water and put a cap of Kents or something similar Iodine in the water and place the coral in there for about 15 minutes and return to the tank. If you start to see the coral deteriorating I would frag the good parts and watch them grow to other healthy toadstools. But try the iodine dip first. Also are you doing frequent PWC
`s to replenish iodine that is being depleted by normal fish and coral processes. If not it would be a good idea.