Kev -

there can be 2 things -

the living conditions are different - one gets better light, cooler place etc than other.

the starters can different - they have some variability - what we call sporting in AVs. Select the best - toss the rest.

It of course depends on the variety - the smaller blooms take less energy than huge - but I would expect 25 and more from most of the varieties.

The best results for me - they are sitting under 4 fluorescent tubes in Oyama pots, I water them when they really dry - and fertilize them sometimes with fish emulsion, sometimes with Peters AV specialty 1/8 of a teaspoon per gallon every watering - and they like to get washed and leached from time to time.

Your conditions are different - but it is an idea what works for me.

Irina