My vote are deer. Need to see more pictures, see the environment where your plants are situated, how big your plants and pots are...but cleanly eaten leaves are usually by deer that aren't so starving. They just adore juicy leaves.
This is just my initial answer to the little information we could use. Please look closer for chewed leaf bits, chewed stems with leaves, leaves with teeth marks, tracks in the potting soil? Do you have rabbits or raccoons?
Are we talking about potted lemon/orange trees? I am assuming they are on your deck, patio or close to the home? Do you know what deer track looks like?
The more we know the better we can give a more accurate answer. Wish we could just BE there like teleported from the Star TreK teleportation deck? Grins! Thanks!
There is deer fencing that is very cheap to install around your patio? It is a plastic mesh similar to bird proofing mesh for blueberry bushes. There are also motion sensor sprinklers to scare anything big enough to cause the sensors to trip...work real well.
Need to get out the detective tools and look just a wee bit closer. To be responsible we need to correctly ID the culprit first before guessing. Thanks...