There are several factors. The different environment is certainly plausible, but it also depends on how much of their physiology is technical and how much is organic. There could be any number of error points that could be affecting behavior. Mechanical "germs" if you will. They could also be suffering from a firmware rollback if their internal clocks are acclimated to their own time. As adaptable as technology can be, there's always a variable or ten to work out.

But when you say they're more powerful, do you mean physically? Or are they equipped with armaments and armor? From the looks of them, they seem quite battle-ready.

So, what is it exactly you are building? A companion creature to these time-displaced [Don't say 'things'] souls?

[Better.]