How to use three CCP modules in compare mode simultaneously in PIC16F?
To do what you want to do, you should not reset timer1.  Instead, when you receive an interrupt from any of the compare modules, write a new value into that compare module equal to the previous value plus the timing interval for that module.  The timer will continue on its way and you will get the next interrupt after this interval, and you can repeat the process.  Make a similar ISR for each of the three modules.  This way, all three modules can use timer1.