My species won't grow

[FrFrancis]

Hi Everyone,
I have been growing orchids for 30 years and so am stumped by my current problem. I have 4 paph species which I bought at seedlings: venustrum, delantii and hirsutissimum, and maliponese. While the plants seem healthy and the hybrids around them are growing well, these 4 have not put out any fans but sometimes grow a new leaf. They grow in an orchiata bark mixture from Quarter Acre Orchids that my other paphs love. They are in an east, north-east facing window about 6 under a growing light and given MU fertilizer weakly once every 2 weeks. There is a Paph Cereal Killer and NoID strapleaf, and an Appletonian growing with them and all of those flower regularly. The venustrum is 5 years old, the delantii is one years old and the rest are 3 years old. Except for the venustrum they were all labeled seedling and expected to bloom in a year.
THANKS