** i have some apartments and now have 2 elect stoves that the burners and oven take forever to warm up when you turn on. **
Did the stoves ever work properly where they are connected now?
Many apartment buildings only have a 208 volt power supply. If you installed regular household 240 volt stove models, the elements will not get as hot at 208 volts. In that case you can either replace all the elements with 208 rated ones (if you can find them) or purchase stove models designed for that power supply (again, if you can find them).
If they did work properly in the same locations previously, there is likely a problem in their power supply. First would be to have someone check to make sure they are receiving 240 volts at their wall outlet.
If their power supply is indeed Ok, checking the internal range wiring would be next. A common place for range wiring failures is where the range's cord connects to the stove's internal wiring.
The wires connected to the main terminal block often become loose and end up melting the terminal block itself. In that case replacing the main terminal block *and* trimming back the connecting wires until good, unaffected wire is found will be necessary.
You can see one common GE range terminal block at the following link: