Hi. As die euphyllia, we can assume only a bacterial infection or the introduction of the reagent into the water. From brown jelly help bath iodine from all manufacturers.
If the reason for the filtration system, it is necessary to check the membrane and resin, all filter elements.
Bacterial infection is contagious. From brown jelly take out euphyllia in a vessel with aquarium water, remove syringe damaged tissue, placed in a container of aquarium water and iodine for 20 minutes ( TROPIC MARIN PRO-CORAL CURE 200ml.) , placed in a container of aquarium water and then return to the aquarium.
Sorry, my English is not good.