Thanks all for your help in this. Update time!
After your advice I dropped the light, moved my flow around, had a good tune up of the CO2, and here is where I am at...
Currently 3 kessils at 65%. I had dropped to 50% but I noticed a definite drop in growth rate, to almost nothing at all. Back to 65% now, algae doesn't seem to be taking over an the monte carlo is sending out runners.
2x Koralia 7000s in the top left corner pushing the same way as the inlet, lots more surface agitation
Moved back to inline atomiser for CO2
Degassed water from the tap is pH 7.40. CO2 profile for the last few days has been (purple lines CO2 on and off, yellow lights just on, orange lights on 65%):
My first question - does this all sound ok? All looks ok in the tank, although the plants aren't doing a vast amount of growing.
My second question - I initially came here as I was struggling with Hygrophila 53b (very slow growth) and alternanthera rosaefolia (leaf holes/melt). The hygrophila is still there, still growing slowly, and the alternanthera has gone completely now. I'm really keen to have a red plant across the front of the longer wood, to break up the greens and to add a different texture. Should alternanthera work now I've got the other things right, or is there something fundamental? When I planted last time it took beautifully then fell apart after about 3 weeks, never to return - I assume after it had used all the nutrients in the jelly?
Photos attached for your enjoyment and in the hope they might be useful.
Thanks as ever.