I've done a 45% water change and the remainder of the fish are fine. My water stats are all perfect now. I did a water change yesterday too due to Sphinxy's problems and didn't do a water test after that - so the stats were before the two water changes.
I don't want to do another water change tomorrow!!!
The four remaining guppies look really happy and although they are flirting a lot the females don't seem to be stressed by it.....do I try and get another female or do I leave it as that? Although if Sphinx recovers I'll need another to at least keep the balance right as I've got really attached to him so I won't want to give him back if he recovers fully. Although now he'll have to be 110% before I try after this incident.
I'm also transporting 5 fish out of the tank on Wednesday as my friend is having them (they were given to me by an owner that couldn't cope but I don't really want them) that should help towards the amonia, nitrites, nitrates, etc too, although they are all fine now.
Maybe two more females at once would be safer as maybe they'll help each other rather than be a 'new fish'!!
Anyone who ever says...."keeping fish can't be difficult" send them to me!!! Especially as my (now paid job!) of taking on ill fish from LFS and trying to diagnose....treat....and then give back!!!
Thanks for all your help by the way.....Oh and......she's actually still fighting.... she still looks weak and obviously is a very beaten up fish but she is actually swimming a bit now...we'll see whether she makes it through the night and I can reassess.