Inconsistent dimming

I just installed my first in-wall switch, a GE dimming toggle (4-way with 2 add-ons), and I’m having some trouble with the dimming. It’s controlling four can lights ( - two in a stairwell and two on the landing above. Everything seems to work as normal until I dim down to a very low level, at which point the two bulbs on the landing get very dim and the two in the stairwell stay at a somewhat higher level. As it happens, this works for us - we need the light to get up the stairs but we want to avoid bright lights disturbing my daughter when she’s in bed - but I don’t understand why it’s happening and if it indicates some other problem. Are we just hitting the limits of dimmability and there’s naturally variability between bulbs? The two that are dim are the ones closest to the master switch.