there are several threads here you can read them in order to get help for these questions .
I think enough fertlizer is the case. looks like they need shelter too.
Repeating myself yet again, the three most common reasons a plant won't bloom are insufficient light, insufficient nutrition, or too much nitrogen.
Vanda leaves should not flop over like that, but be stiff and "spiky" pointing outward from the center. Hers looks like it is being grown too shade, possibly with both of the other two applying as well.
I don't grow many dens, but I'd bet that's the problem with that, as well.
If you can find out more about her growing conditions, watering and feeding regimen (fertilizer formula, how often, and at what concentration), it would really help.
Don't let he just move the plants into direct sun - they have to be transitioned, or will burn.
HI Lilandra
I grow many dendrobiums here and I have most of them in full sun. They are doing great. I even have on that has been blooming constantly for over a year now.
It's my personal belief that they need a lot of sun or at least partial sun.
To add to Ray's observations, while light may be an issue with the Dendros, if they are deciduous types (the first appears to be) and it is not given a rest, it will hang on to a few top leaves, but not bloom. If we knew what the species (or types were) we could respond with more authority (that means better guesses!)
I don't know specifics about types. I don't know how I would find out... Mom uses terms like air vanda, sun vanda, water vanda ;-)
A couple were gifts from my sister's friend.
About location:
They're outside in the tropics.
The 1st and 4th are now hanging from the eastern side of a shed. In front of it (about a feet away) is a fence with a stand growing little plants. So I think it gets almost direct sunlight.
The 3rd is hanging on the eastern side of the house...outside...from the eave...nothing really blocking it...just a wire fence.
The 2nd is currently hanging from the western side of the shed.
I can take pictures of location or anything else.
I'll try to find out more about the feeding and watering regimen and maybe the 4th has flowered before (?)
I'm just guessing here, but the Dendros may be deciduous and may be getting too much water/fertilizer during winter when the dry season normally comes. If so, I suggest telling your mom to follow the rains. When it quits for the winter, quit watering the dendro. But this is based on it being a deciduous dendro. We really need to figure out what it is.
we don't have winter
we have rainy season (about june to december) and dry season (about january to may; but it still rains just not as much and not as often...maybe)
I believe those folks were right. Your mom's orchids need more sun. I have half my vandas in the full sun and other half in very bright light (under 50% shade cloth).
those Dendrobiums will flower for you if you give 'em more light. All but my seedling dendrobiums are in the full sun.
What part of the country are you from anyway? I'll be glad to help when I get the chance.