leopard geckos not well

Question
My son purchased a baby leopard gecko in June.  On our next visit to the pet store they gave him a full size leo gecko from a rescue. She said they could be housed together since the adult was a female.  We were told that it was healthy but was having a problem shedding.  Over the past 2 months the adult has not been eating properly if at all.  She has become very thin and still can not shed by herself.  I have gone to several pet stores, vets & animal rescues to see what may be wrong.  I was told everything (impaction, detached retina, parasites, stress).  I was advised (by a vet tech) that if the larger gecko has a parasite it is not transferable to the other lizard. The baby has been thriving (eating large amounts of mealworms & crickets) until last week.  Now it appears the small gecko is not eating & its tail is thinning.  Now I think they are both sick.  I can't get any help from the pet store or the rescue that provided the sick gecko.  I am not having any luck finding a reptile vet in the area.  One said I could do a fecal exam but the lizards are not pooping.  Can you help?  addtl. info:  25 gal tank with 1/2 calci sand and 1/2 paper towels, 24 hr tank heater on 1 side and 75 watt clamp lamp during the day (temp ranges between 80-90+ during day and down to 70's at night.  small cave, fake plants, driftwood, worms, crickets & water 24 hrs.   Thank you for your time

Answer
Hello Traci,
That is inaccurate regarding the parasites or worms.  They can transfer to each other through fecal to oral routes, etc.  It is best if one is not doing well, to house her separately until she is doing better.
I would get the calcisand out as that can cause impaction if they have ingested any of it, plus, since they are sick it harbours bacteria.  Use paper towels right now, they are easy to clean up.
Everything on your setup sounds good, actually, excellent job on the setup.  
If you cannot afford another tank, maybe just put a divider in the tank so they are separated & get another undertank heater & basking light & cave so each side has their own setup.  
Right now, I would feed them some chicken babyfood along with a pinch of calcium & some pedialyte added in.  Start with 1-2 ml's for the adult, & .5-1 ml for the baby.  Use a plastic syringe & gently use a swab to get the mouth open & quickly squirt the food in.
You should be able to get a fecal out of them feeding them manually in that manner.  If you cannot find a reptile vet, try looking here:

www.herpvetconnection.com

If not, any regular vet can do a basic fecal on them both to determine whether or not they have worms or parasites.  That is what it most likely is, or even flagelletes or amoebas perhaps.  

Let me know how they are doing.

Tracie