One thing about nems is the common sense logic, bigger is better/healthier, or splitting reproducing is sign of success does NOT apply IMO.
Often bigger means they are wanting more light/energy, and you provided that w/ spot feeding, so I would expect them to close a lil, but maybe have brighter color.
I actually think you are having reasonable success just going off post/no pics.
FWIW both my sebae/crispa and LTA/doreensis did not get spot fed first year and a half, and they both became huge healthy monsters, had em 5 and half years before downsizing system.
I noticed both actually got smaller w/ better light and spot feeding, or at least less stretching.
Some do not spot feed at all, or rarely to prevent excessive growth, light is their main source of energy anyway.