Ok my boyfriend and I are new to fish (we have a snapping turtle that we have kept successfully). We decided on bettas because we liked their attitudes and their beauty. We bought nataku a week ago and he seemed irratated in a smaller tank (2 gallons) so my boyfriend put him in a 10 gallon tank with a fake tree and he seemed vert happy and lively. Last night he boutght him a heater and we raised the tanks water temp to around 75f (mostly because the room we have them in is really cold). His tank was already at this temperature, but we needed the heat lamp back for our title. We was fine when we put the new heater and filter in. When we woke up in the morning to feed our animals he was at the surface, lucid, had white spots on his head, and his eyes appeared bigger. He wouldn't eat the food we normally feed him and he went into the tree and wouldn't come out. I managed to get him out from the tree and I did a total water change and took the filter out . He seems a little better, but he's still laggy and I'm worried about the white spots. The only additive we use is to make tap water safe. Any help would be greatly appreciated. (also my betta seems fine.. He's in a smaller tank and we use the same water treatment and food).