Do I need to shock if losing chlorine?

Im using one of the Taylor drop based test kits where when doing the CC test the color turns "pinker" if CC is present. Problem is that Im not seeing a noticable color change. I am batteling a constant chlorine loss of 4-6ppm and sometimes more. I'll add two gallons of bleach at night, which should put me at 8ppm and in the morinig i'll have a reading of 2ppm sometimes even 0. Water is crystal clear though. Weather has been crappy her the past few weeks so the pool get little use. Solor cover is constantly on.

Should I be shocking if having a continual ch loss?

Thanks
John

24ft AG vinyl 15k gallons
FC 4 (just added a gallon of bleach this morinig, before that it was 1)
CC ?
TA 160
PH 7.5
CYA 60(raised it from 50 to try to maintain my CH level)

From what I have read here, if you are loosing chlorine over night, then your chlorine is killing off bacteria, etc. So I would shock it according to the best guess chart untill you loose little or no CH over night.