Some photos would help, and a name too, if it came with one. Many plants can be classified as an "air plant." So no one can really be of much help without at least a photo of the plant(s).

Here is a pic. I'm not sure the kind, as I bought them as a mix lot from a place called Plant Oddities off eBay. This is my first time getting live plants off the internet. I've had them for about 2 1/2 months. I have not fertilized yet as the instructions said to wait for 3 months after arrival. If you need any more pics please let me know.

Your plants are Tillandisa -- though what species I have no idea.

It is not necessary to hang the plant upside down after watering to drain away any excess water. Water quality is normally not a big issue.

However, air circulation is a very big issue. Most tillies require very good air circulation. Your problem may lie here. You said that the base of the plants is were the problem lies -- that they are going "brown and mushy" there. Notice that those are the same areas you have shoved down in the shotglasses. Air circulation there will be utterly, "crap-tacularly" poor. As a result of the stagnant air, the plants may have developed a fungal or bacterial issue. IF that is the core of the problem, then you will need to remove the dead material (pull off any dead brown/black leaves, & cut away any brown, mushy material .... use a separate sterile blade for each plant being treated). Then treat the affected plants with a fungicide. I have never needed to do so, but Bayer makes one for use on roses that may work -- read the directions before applying. If you wish to continue use the shot glasses, then add more marbles so the plant's base sits at the top of the shot glass. A dab of hot glue can be used to affix the plant to the top marble so it stays put. An alternative would be to affix the plants to pieces of rock, wood, or whatever appeals to your tastes. (If you go that route, watering with a spray bottle should work fine.)

Fertilizer: Tillies are not "hungry" plants ... they don't need fed often. Use a dilute fertilizer solution.

Lighting: Based on what I'm seeing, I suspect lighting is going to be an problem for your plants sooner or later. Tillies generally like very bright light -- and where you have them currently the light definitely is not. If you wish to display them where they are, a lighting system would be impractical. You would likely be better off growing some on bright windowsill and rotating those out with ones on the shelf once a week.

Hi savannaicus :)

Could we get a close up of one of their bases? Or you could try to observe yourself if it looks like they are rotting. Your watering schedule partly depends on the humidity in the room and if the air is not stagnant. There are many different tillandsia species, so seeking out an ID for them may help you better care for them. They all look like tillandsia ionantha of varying cultivars to me...but i don't ID stuff very often.

I've discussed fertilizing in the bromeliad forum, and the consensus is they really don't need it...and you risk overfertilizing. Supplying better airflow, if its stagnant, would improve their health more than fertilizer.

The bromeliad forum may be able to ID them, or name that plant forum, but the former can also provide advice from experienced tillandsia growers.

Here is a link that might be useful: Bromeliad forum

You want to duplicate them being out in the open in (usually) humid regions where there is plenty of light and air. They put up with being perched on trees, telephone poles, cacti etc. with no contact with the ground in order to be in the sun. Watering is accomplished by fog and rain falling on the leaves and running down to the leaf bases. Usually dry tops in a typical poorly lit and often arid household interior are probably not going to produce a successful outcome.

There are some species that grow in coastal deserts where the main source of moisture is fog, but even then the fogs come often enough to make their growth possible. Perhaps much of the year these occur daily. And I don't know how many, if any of these desert Tillandsias are in general cultivation. Most others would be coming from climates where it rains a lot - a lot more than once per week - for at least part of the year. For instance Florida, with its afternoon downpours from June to November.

Thank you all very much for the advice. I removed them from the shot glasses and placed them on the window sill for now. I'm going to try and buy a wire suction cup soap dish for them so they can live by the window and get lots of air. The bases of the rest look pretty good, but when I get some natural light tomorrow I"m going to check them better and get the fungal spray just incase. I hope I can save the rest and buy a few more down the road. Thank you all again!

I have found success with watering my air plant (or tillandsia) once every two weeks. It seems very forgiving if I water it too much or too little. One time I did not water it in a while and the bottom started turning brown and one leaf fell of. I promptly watered it and it became healthy again.

I also give the plant a little shake while upside down to get extra water out but I have not found a need to hang it upside down.

However, what you have sounds like rot. Mushy and brown is not what I had, only brown. When you say they turn brown and mushy when you water them do you mean they remain brown for a few days? Hours?

Do you let the water you use to water these plants sit out for a while, say over night? This lets the chlorine evaporate so that it does not harm your plant. I suspect that tillandsias are more sensitive to chlorine because it lands on its leaves.

I don' see a problem with your set up but you might want to try something new and see if it works better. Something is not working for you, try an experiment if that is the kind of thing you would like to try. Something needs changing to keep the plants healthy.

Are all of your plants having this problem.

I wish you success in growing this wonderful plant.
LG.

I started out with 15 plants and now I"m down to 7. The remaining 7 are living on my kitchen table right now, and seem ok. I have well water so I've never needed to let it sit out for my other plants but I will give it a try for these guys. The ones that I have lost I could not tell they were dead until I gave them a dunk in the water, that could be due to my inexperience with the plant however. Once wet They bottoms I could tell were rotten and the leaves all fell off in my hands. I'm due to water these guys again so I will leave the water out and if anything happens to these I will take pics before I discard them. Thanks again!

It could be the water. Tillandsia take in nutrients from the air and rain water. I've heard that trace elements in drinking water, spring water, well water...any water that comes from the ground, are harmful to the plant....but i did spray them down with a hose a couple times before and have not witnessed any adverse effects...but maybe i didn't do it long enough or my city water doesn't have enough copper and what have you in it.

Sources on tillandsia care usually state to water with distilled...and some say RO water as well.

At first i submerged my tillandsia for several minutes....and i can't remember where, but someone brought up a good point on why leaving them in the water for a while isn't good for their health.
Now every so often i heavily mist my tillandsia until completely wet, then gently shake off excess water while holding them upside down to prevent rot.