It's in shock from the light and environmental change. It could be water logged too, not sure what type of soil you have it in. Why did you bring it inside when the temps hit the 70's at night? My trees are outside during the winter here where it hits 30 degrees for 2-3 weeks during the evenings. 70's should not and will not hurt you citrus trees. I would put it back outside Until you are consistently hitting the mid 40's in your area. Just my 2 cents. Here is a pic of my Mexican key lime tree.
Evan

Cold snaps? If the growers down here in Florida worried about the 70's we'd only have pics of oranges in museums.

I'd start watching the temperature when it dips into the mid 40's.

I wonder if the soil is staying overly wet / waterlogged.

I think it may be too much water. The water has not been evaporating as much as before (possibly b/c I brought the plants inside).

Evdesert, I have them in MG Citrus, cactus soil. Should I bring them back out? Will they survive the wilt? The leaves are not dry yet.

I am not a big container citrus person, all of my citrus trees are in ground because I live in the desert southwest. If it were me I would put it back outside and change the soil it is potted in. Do a search on Al's gritty soil mix or 5-1-1 soil mix here on the forum and get that tree into a lighter more porous mix, others on the forum have had a lot of success with these soil mixes.
Evan

Miss, this is root rot. Your tree is way to wet. I would suggest you re-pot it right away, to see if you can save it. Use a very well draining mix. What you're using is much too compact for citrus. Most container citrus folks on this list use the "511" mix. You can search the forum for the recipe, it is very easy. It works quite well. Once you start to see some recovery (new leaves starting to flush), be sure you fertilize your tree. Again, most of the container citrus folks on this forum prefer to use Dyna Gro's Foliage Pro, and will use it full strength with every watering, then 1/2 strength during the winter months. You will want your citrus trees to remain outside as long as possible. When temps start to threaten to drop below 32 degrees, it's time to bring in your container citrus. Container citrus will be more sensitive to cold temps that citrus trees in the ground because their roots are not as protected being in a pot. And, the Mexican lime is one of the least tolerant citrus of cold temps So, if your temps really are going to hit the high 30's, I would bring the tree in. You never know what YOUR temps will be, exactly, unless you have an outside thermometer or weather station and are tracking your temps, to compare to what the weatherman is telling you.

Patty S.

What cold snaps?! 58 F. minimums are not even a cold snap in San Juan.

How cold was it, as Johnny used to say?

Oh, I see yours are now IN the house! LOL.

Maybe heat exhaustion.

NJOasis, it hasnt been hot around here. There was a very hot/humid 1 week then temps dropped about 20 degrees in about 2 days.

I'll look into the 5-1-1 mix.

oh its dead. that's the problem.

Miss, I suggest you do it very soon if you want to save this tree. As Ryan has mentioned, it does appear to be dead/dying. I would get it re-potted yesterday. Heat has nothing to do with what's going on with your tree (save for the fact that perhaps it induced you to over water the tree). It is root rot. You'll know the minute you re-pot. the soil will not smell good, and the roots will all be rotted away. Citrus are amazingly resilient, though, so if you get to this quickly, you have a chance of saving your little tree.

Patty S.

Thanks Everyone. I will post the progress once up and running.