Do you still have them bagged? And, if they are bagged do you have the bag open or holes in it for air exchange? These filiformis.filiformis NJ seedlings are roughly six months old. They started out in this exact same spot sitting to the side of a LED grow light (you can probably tell by the shadow inside the cup). They are growing in either 16 or 20 ounce cups (I can't remember which
) filled with Better-Gro sphagnum moss. They sit in a tray with anywhere from 1/2" to 1-1/2" of water in it. Beside them is a large tray that holds some pots that I'm *attempting* to grow some sarrs in...an inch or two of water is in the bottom of that roughly 16"x16" container...so another humidity source.
When these were roughly 1/2" tall I removed the loose-fitting plastic cover from them (a piece of clear bag) and they've been dewy ever since then. I believe that that the "climate" around them is humid enough for them now...my little temp/hydrometer that sits at grow mix level in the neighboring box usually reads something like 65% RH on average. In the individual cups the soil level is below the rim...I believe when the lights (and thus a little fan) are turned off that it creates it's own humid micro-climate in that area. (For transparency, I'm in lower Alabama and just now checking the outside humidity it's 83% under partly cloudy skies. Your growing area might be more arid and require different actions to get the humidity up.)
As Chef inquired about how long you've had these it may just be that they've got to settle into their new home. Being low growing and the sphagnum moss staying good and moist I'm not sure I would be bagging at this point. Light is tricky, though, too much and you burn them...too little and they don't produce a lot of dew and they suffer. I think they really need to just settle in.