Why is one TimerTask slowing down another?

I have got a Timer Task, which updates all player positions:

public void run(){
    {updateWatcher = new TimerTask() {
        public void run() {
            update(0.1);
        }
    };

    t.scheduleAtFixedRate(updateWatcher, 5, 5);}

And I also have another TimerTask right under that one, which updates all projectile positions:

UpdateWatcher = new TimerTask() { //Different variable. Note the capital U.
        public void run() {
            for (Bullet b : bullets){
                b.update();
            }
        }
    };
    t.scheduleAtFixedRate(UpdateWatcher, 5, 5);
}

However, the second TimerTask is slowing down the first one. If I delete the iteration, like this:

UpdateWatcher = new TimerTask() {
        public void run() {

        }
    };
    t.scheduleAtFixedRate(UpdateWatcher, 5, 5);
}

The player moves at the correct speed. However, as soon as I re-add the code (using Eclipse de-bugging to add it live), the delayed task executes a lot less often, causing players to be moving more than 10 times slower than usual.

What could be causing this, and how could I fix it?

via Chebli Mohamed