If when you repot your plants you are very careful and tender with them, they will not be shocked at all. There is no reason to shock your plants under a normal transplant.
Once when I was having trouble with a crop in soil, and I final told myself, SCREW THIS!!!! I am putting them in my Hydro system. What I did was took the plants out of the pot, very carefully loosened the soil, and then with slow moveing luke warm water i washed the roots off of 90% of the soil, then stuck the 4 of them in my hydro system. Not only did they not wilt, but they took off like a bat out of hell. Most all plants can be the ultimate timex. Takes a beating and keeps on ticking. I do think that repotting is in order here though. Among a few other things. But not enough information has been giving to make an educated answer to his trouble.
We do not know what soil he is useing, what nutrients he uses, how often he waters. HELL... we know next to nothing about what conditions his plant was under before he left, let alone while he was away. Anyone can take a guess at what his trouble is.
OK.. I have my answer for what is wrong with his plants. Aliens from another Galaxy landed in his back yard with a bad case of Space Hemroids, and they found out that by rubbing his plants on their ass, that it releaved the burn and itch. By accident, these aliens rubbed these plants on thier front side also, hence they have been over nutt'd.