Good morning everybody! I am having a lot of issues with my tank, which is costing me an arm and a leg. I feel like I am doing everything correctly, but clearly something isn't just quite right! I own an AquaOne 200L system, with a filter sock, a BubbleMagus Curve 5 Skimmer, and a Pellet Reactor for filtration. The heat is also set at 26C, and I keep the salinity at around 1.025. I have a test kit at home for Nitrites and Phosphates - Both which only show a small trace - Something which my LFS has said is not the end of the world. Well, at Easter, 8 weeks ago, I went home to my family, and left my tank on its own for the week. I had a Magnificent Foxface, Yellow Tang, Dwarf Fire Angel, Coral Beauty, Royal Gramma, 2x Clownfish, and 5x Green Chromis, and One Chalk Goby. For my cleanup crew I have 2x Cleaner Shrimps, 1x Blood Red Shrimp, and some Turbosnails and 6 Hermit Crabs. For feeding the fish as I was away I also put three 'Holiday Feeding Blocks' in the tank - which said they were marine safe. When I got back from my holidays, Dwarf Fire Angel, Royal Gramma, and Clownfish had all died, with the Yellow Tang, Coral Beauty, and One Chromis. The Foxface had also contracted what appeared as 'Black Spot' - So I ordered some PraziPro from the USA. This left just the Foxface, Chalk Goby, Four Green Chromis, and the Cleanup Crew Left in the tank. Unfortunately, the Foxface died the day which the PraziPro arrived, and the Chalk Goby got what can only be described as an 'Infection' on his side (Which looked like internal bleeding)... He died the same day. The LFS told me that the Holiday Feeding Blocks can be Toxic for the tank, and as well as that, drive the parameters crazy - the probable cause for this... So, this left me with just 4 Green Chromis, and the Cleanup Crew... Which I have had alone in the tank since the Crash, and have been doing fine! Also, I must point out that I have some corals in the tank. Some Mushrooms, a Toadstool, A Torch, A Duncan, A Hammer, and some Green Star Polyps, all of which are thriving, growing, and are 'out' most of the day until the lights go off. In the time I left the tank after the crash (With just the 4 Chromis, the Corals, and the Cleanup Crew), I have observed many Brittle Starfish, Asterina starfish, and Amphipods in the tank, all which showed me signs of good water quality, and a tank which has settled down since the 'Crash'. Also i have had some 'FeatherDusters' appear and grow in my tank. It had also been around 6 weeks since the crash, so I thought any diseases would have died off. After some more water changes, and constant monitoring of the tank, I thought it would be a good idea to introduce some fish back into the tank slowly. So around a week ago, I brought myself another Goby, who has been sifting through the sand ever since. As the Goby was doing so well, and parameters were fine, just three days ago, I brought myself a pair of Clownfish, as the next fish to introduce. As always, I drip acclimated them, and put them in the tank. They have been eating VERY well, and seemed to enjoy their new tank. I actually felt like everything was going so well... I woke up this morning, and the Clownfish look to have contacted what looks like WhiteSpot (See Attached Image). And not only that, the Goby has seemed to have gotten a similar infection as the one I had before the crash (See Attached Image). Literally overnight, the Clowns have contracted whitespot, and my active Goby has got this infection, and has deteriorated. What is happening to my tank!? The Chromis are all fine, as are the corals and my Cleanup Crew, but it seems any other fish I have added seem to get complications? I have just dosed the tank with some PolypLab Medic and some Garlic XTreme for the Whitespot, and I am about to do a large water change. I'd appreciate any help - as this is all starting to get expensive, as well as upsetting!