Could the lights be the sole reason for the plants lack of leaves , i suppose so.My Phal's tend to have less leaves than the 1's i have given to friends & family, they grow in windowsill',s , me under lights & in the greenhouse.I believe the plants require less leaves under my care because they have plenty of light all year round & my hybrids tend to grow a new leaf then spike, this can be twice or three times a year.Whereas my friends/familys Phal,s tend to spike once & maybe grow a couple of leaves in between flowering.
Reducing the light(less hours/lower levels) under lights may make the plants grow more foliage to compensate but also a change to other growing variables may achieve the same.
Personally if the plants under lights are healthy & still flowering then i wouldn't worry about them to much , maybe give them a holiday in the greenhouse every now & again.