http://www.hobartservice.com/Manuals/
You can get a service and repair manual form the above link.
The only way that something like that could happen was if the wiring or switching was faulty. You see an element is simply a Big Resistor/Resistance, that gets hot when electricity is passed through it, the amount of heat is a function of the resistance and voltage/current as opposed to resistance, the less resistance and More Voltage and current the hotter something will get. to a mathematical point which it cannot go beyond.
Now all the elements in the any toaster are all the same resistance, and as such, can only get so Hot, and use so much energy. So they should be all the same...
Now if as you suspect, one element is "
taking power away from the other 3 elements" (sic)
Well now at first glance everyone would say Oh NO WAY.. But in fact.... WAY.. This is indeed possible, and I have seen it myself. Here's how it can happen.
What can happen is an Element can have it's element winding wires touch together, (Often caused by people using a fork or a knife to get something out of the toaster) well, usually, they just Blow the wires apart, but occasionally then they Fuse them together, (Sometimes they can and do spontaneously touch, as the wires sag with heat and age) Now when they do this, guess what, the resistance of that Element goes DOWN, which means the Current will rise, as the Voltage is constant, and Now this Element WILL BE and Appear to be in fact Hotter than the "Other 3".. and while not exactly "Taking the power away" it is dispersed in a Non-linear fashion due to ONE elements resistance being Lower will glow hotter than the rest.
The Fix, well replace that element.. ya will be good to go..
Also stop putting forks and knifes into the toaster, as this is usually what does it...