Fish Feeding Advice Please

Ooh I see Sue replied whilst I was dawdling!

Thanks Resa.

Jesnon, I hooked the poorly fish out into my quarantine tank as soon as I saw they were ill so there's no chance of dead fish polluting the tank.  There may be a chance of some residual infection I suppose but the remainder are acting fine (apart from the one bully). 
Levels are tested daily and are constant at 0 NH3, 0 NO2, 5-10 NO3.  They've been the same for almost a month now.
Daily feeding is now the equivalent of 1 large flake ground up (and pre-soaked) with the occasional treat of 1/4 tube of strained brine shrimp once every few days.  I'm keeping the open tube "clipped" shut and throwing the last half tube away as I don't want it going off.  It's the safest option I can think of until I get some frozen shrimp and cut appropriate sized bits off a cube.

Sue, I'll go for your Option 1 and add 3 more to bring the shoal size up to a friendly level.
I see now why they say Tetras are one of the worst fish to add to a new tank!  If I'd known that before I wouldn't have chosen them but now that I have I suppose I'll just have to persevere and hope that the fittest will survive so I end up with a healthy shoal of at least 6.
 
The good news is that the Endlers are active as ever.  One of them doesn't mix well with the hyper active trio of larger ones but at least he's swimming around rather than bottom-hugging like before.

Many thanks all,  I'll let you know how things progress...
Ken