Growth abortion and size issues in Lepanthes.

[Flowers]

Good day everyone,
Almost all the Lepanthes I have seem to be aborting 95% of new growths. In addition to the abortion, the growths that make it to maturity are always substantially smaller than those that preceded them. Plants with these problems are L. imbricans, L. ophelma, L. pastoensis, and L. caprimulgus. The bizarre thing is that they are all flowering profusely. I mean a lot of flowers, sometimes on multiple spikes.
The three Lepanthes I have that are not experiencing problems are L. gargoyla, L. telipogoniflora and L. tsubotae. They are doing astonishingly well.
They are all growing in a terrarium (Exoterra XL high terrarium) with two small 9v PC fans(will upgrade soon), humidity is maintained above 88%, temp (F) is at roughly 72 degrees day, and 65 night, fertilized weekly with 1/4 strength Grow More 20-20-20.

There are several other plants growing with them, including Masd. caesia, Pleuro. teaguei, and Pleuro restrepioides, with the two former having the same size decrease as the lepanthes, and the latter having no problems what so ever.

The abortion is obnoxious, but the decrease in size of successful growths is down right depressing. Anyone have any ideas? I'm willing to try anything at this point.