Since this post the guppy I posted about died that day, as a result I had a slight ammonia spike and since then the problem has got worse. With that ammonia spike (I'm hoping) another guppy passed away the following day which again spiked ammonia further and subsequently killed yet another guppy the day after that. By this point I'd had ammonia spikes each day due to fish death, this later went on to kill a glow light tetra on the 4th day after the first fish death and a Platy on the 6th day. My tank is rather good at cycling out ammonia within a few hours but on the downside my nitrite is now sky high and I am in the process of lowering it. To recap, I believe I know my plan of action with trying to turn my tank around but the fish deaths still somewhat remain a mystery. There were no physical marks to indicate any disease, even guppy disease, however to have 3 guppies, 1 glow light tetra and 1 platy die within the week is far too strange for me. There was no question about my water parameters prior to adding the guppies, it was perfectly fine for all levels but the 1 fish death has ultimately thrown everything out of balance. Any advice is appreciated.
Nathan