Yesterday evening, I was out grocery shopping and visiting my mom for maybe 3 or 4 hours and I came home and one of my guppies eyes looked like they were bulging out and had blood around them. He was swimming in circles as well. Maybe an hour after I found him(and separated him in case he was sick) he died. I don't know if he got sick suddenly and there was nothing I could do or if the others tried fighting him since there were red spots on his back? Or maybe he got stuck somewhere(Not sure where he could have gotten stuck at though). The other guppies are completely fine from what I can see however. I have 11 guppies now in a 10 gallon tank. I was told when I got them that it was fine since they were little but now I found out it might be over crowded but I don't have any other place to put the little guys. I have a heater, a filter, and the floating thermometer. The water has been treated and such but I may have added them in a bit too early. I did a 5-N-1 quick dip test strips and these are the results. Nitrate- 80(unsafe) Nitrite- .5(caution) Total Hardness- 150(hard) Total Alkalinity- Test got a little fuzzy so it looks like either 180(ideal) and 300(high) pH- also got a little bit fuzzy here so between 7.2(neutral) and 7.8(Alkaline) I'm not sure how accurate these strips are because they are from when my brother had his tank up and I can't recall how long ago that was. Possibly up to 1.5-2 years. I just really want to know if the others are going to be okay. And with the test result, best way to adjust what needs to be adjusted.