My flute won't play any notes that require the right hand keys. F, E, and D won't come out on the lower register. Is there anything I can do?

There are no leaks and the rods aren't bent. I'm not really sure what happened, it was playing fine and then all of the sudden just died. Can anyone tell me a reason for this?

Take it to a repair tech. Most likely it's a leak in the region of the F#/F/G keys. Play the same notes (F, E, and D) in the second octave.....Do they come out there? If not, have it checked by the tech. If they do, and you sense no problems there, it could just be a matter of experience. The low range is very often the most difficult to play, especially when you're relatively new, so it may also just be a matter of learning how to use your air to produce these pitches.

How can you be sure there are no leaks? Did you use a feeler to check the seal?

I can play my chromatic scale full range, so there's no experince issues. That's what I was actually trying to do until it just didn't play it..

A sealer? Where can I get one of those?

feeler*

Maybe it's because of too much spit? :/

There's no such thing as a sealer. A feeler is the tool that is used by repair techs to detect leaks. It's proper use and construction is very difficult to communicate over the web, though I've tried before. If there are no experience issues, then it's a mechanical problem with the flute (almost certainly a leak). Take it to a repair tech and let them tell you for sure, as over the internet, without seeing the flute, it's extremely difficult to be sure.

I can only hit in the higher register... the lower and middle won't come out at all :/

Spit can get into the toneholes, forming a bubble that seals it off, so that could be it. However, for this to happen on a flute is pretty unusual (not unheard of, just very unusual). It's mostly a problem with the smaller toneholes (like trill keys, or those found on a piccolo). A quick visual inspection should tell you if spit is the problem. If it is, just blow it out of the tonehole.

What exactly causes leaks?

If you can only hit the upper register, it's probably a leak like I said originally.

There are tons of things that can cause leaks....Here are some big ones:

1. Changes in the pads, such as swelling due to the absorption of moisture, or cracking because of extreme dryness

2. Changes in the way the pads are seated.

3. Damage to the mechanism through mistreatment or neglect.

4. Leaks can open up purely from playing, especially if you play often and hard.

Gah, I think it's the 4th one.

This isn't my flute, mine is in the shop for repairs so I'm using my friends. She's not really into playing it much, so she only plays during band (which isn't often) and doesn't go home and practice. Me on the other hand, I practice at least 2 hours or so each day or so :/