l293d is not able to drive two 300 rpm motors simultaneously I am using l293d in a line follower but recently I am facing a problem. my l293d motor driver is not able to power 2 300 rpm motors simultaneously while with one of the motors at a time it works perfectly fine. Earlier it used to drive both the motors at optimal desired speed but recently its posing the above mentioned problems. I have tried replacing the Motor driver and Arduino itself but nothing worked and I am still facing the problem.
Check if both channels are working in either direction individually. 
Check the current draw under the load per motor using an Digital Multimeter as an Ammeter function.


The L293 is designed to provide bidirectional drive currents of up to 1A at voltages from 4.5V to 36V.
600mA per channel for L293D


As long as your motors at drawing more than 600mA per motor, it should work fine.