need some help

[landscraper]

Ok, I have been trying to figure out why my PH is a little low.. its about 7.8 it seems from my API PH test.. Here is other info.
SG 1.025
temp 80
ammonia 0
nitrite -0
nitrate 10
Calcium 470
KH 143.2-161
Use RO water
Anyway yesterday I added two filter socks of CC to my sump. withing 3 hrs the ph was at 8.4 but this morning it is back down... can someone help me out? or is this even a problem I should worry about?
Thanks

 

[nikesb]

ph swings happen throughout the day. they should be highest right before your lights turn off and lowest right before your lights turn on.