Hi, young lady,
It is un-professional for a qualified teacher, who is not your coach, to be giving advice on your performance. The watching of videos is okay if you want to get ideas on expression and presentation. In your particular case this is not the problem, in fact, you express your work quite good for a dancer in this grade. A credit to you and your coach. The advice I'm going to give is not for you but to all the lower grade dancers who may have a similar problem to you which is the lack of being grounded. This is usually the fault of not having floor contact, so:
1) The dancer MUST have foot pressure to the floor whilst transferring the body weight. Don't dance above the floor.
2) Discuss with your coach the beat values and on which part of the beat the transferring of body weight occurs.
3) Finally, if you don't have lessons in ballet then start!
The above are just generalizations which would improve the majority of dancers in your grade.
Postscript. Your coach has done excellent work with you and your partner to get you this far. Have faith in him/her and please be patient.