I want to start off by saying I have been trying to house something in this tank for close to a year and a half. I buy fish and they just keep dying ( mostly guppy’s). I worked some things out finally and thought I had my tank finally ready for some fish. I went and got 4 guppies and 4 gosht shrimp to put in my 10 gallon tank three days ago. Everything seemed fine the first day but the second day my cobra male guppie started staying at the top and my assorted yellow male started staying at the bottom with his fins down and rapid mouth movement. I also had two shrimp dead. I decided to test my water and my ammonia was 0, nitrite was 0 and Nitrate as a little bit above 0 but less than 5. My ph was very high. My tap water has a higher ph because I am on well but I have raised many fish in the past and my tap water has never been a problem. What confused me was all my other levels were correct but my Ph was and high and this is a fully cycled tank. I have also done multiple water changes because of my aquarium dirt to get everything balanced. On day three (today) I wake up and my yellow assorted male guppy has a sore on its back I think maybe one of the shrimp did that because it was staying at the bottom but I don’t know. It never had any signs of a sore before. My cobra male guppy is still at the top but seems to be turning on his side but then he rights himself and I think he is stuck floating up there. My other two guppies seem to be the only ones doing well. The tequila sunrise male is doing the best and my orange assorted male is doing good but his fins are down and he has some rapid mouth movement. But they are both eating unlike the other ones. I have added PH corrector to the tank for a short term solution but I don’t know what needs to be fixed because all the others levels are good. My two sick fish have been moved to a hospital tank where I put some E. M. erythromycin to help with the sore as well as some water conditioner to reduce stress. I suspect maybe my water is to cold as well. I have a heater that is set at 78 and I can’t change it. At this point I don’t know what to do please HELP!