Variegated plants usually come from a mutation of sorts. The mutated plant is observed, collected, propagated and marketed. However, variegation may not last forever, and these plants sometimes revert back to their original solid green (called a "reverse mutation"). The solid green doesn't spread like a disease and there is nothing you can except prune out the parts you don't like and maybe freshen up your plant mass with some new plants. 

The growth appears to be seed heads after blooming. Growing through the A/C unit may have stressed the plant and prompted it to put on seed faster / earlier than the rest of the mass. Again, nothing to do (except you really should pull the plant out of your A/C unit).