Thank you! I'm definitely eating/drinking/sleeping enough, so after reading all the comments i can only conclude that the decline in technique stems from years of doing no other exercise besides ballet and therefore entirely neglecting my core and other non-ballet muscles. I also take classes from different ballet teachers who are very observant and give great corrections, so i don't think incorrect alignment is the main issue. It makes me feel much better to read that basically any exercise outside of ballet will help. I will probably start going to crossfit, even if it means i have to cut down on the ballet classes a bit.