Pics would help. You put them out in 50s during the day? Did you leave them out overnight?

Lemon tolerates lower temperatures than lime. That could be the reason for the different reactions.

Certainly, could be a combination of things. I would guess that shock from light transition from indoor to bright outdoors is a big factor. Any of the leaves looking scalded?

it was upper 50s in the day and I brought them in because it was supposed to get down to 37.
the leaves that fell off look perfectly healthy.

Waterlogged roots will cause leaf drop (and the root rot that quickly follows). Does the water flow easily through your mix? Have you checked moisture (wooden stake into soil) for water perching? Were you using the same watering amount for indoors and outdoors?

I have only had them for a week. They are strange. The lime tree, which is the one that lost its leaves, has very sandy soil and the water just runs straight through and out the bottom. The Lemon Tree is complete opposite and the water never does run out the bottom. They are in identical sized pots and the Lemon Tree feels twice as heavy as the lime because of all the water in the soil

They have apparently thrived like this at the nursery but it feels like they may needed repotted. I watered the lime day before yesterday and it is already dust dry.

You need to soak the root ball with the pot in a bucket until all the air is driven out to get rid of dry soil the watering bypassed.

Steve