Lightning?full node question
If it is only the balance of your channels that is changing I would assume that your node is routing payments. The lightning network is all about forwarding payments. 

So the following explains what could have happened assuming you have two channels to a node A and a node B: 


  (A)--20sat------40sat--(you)--30sat------50sat--(B)


meaning:


node A has 20 satoshi
your node has 40 satoshi + 30 satoshi = 70 Satoshi
node B has 50 satoshi


Let us assume B wants to pay 15 satoshi to A this does work via lightning and via your node. The channels will update their balance: 


  (A)--35sat------25sat--(you)--45sat------35sat--(B)


meaning:


node A has 35 satoshi
List item
your node has 25 satoshi + 45 satoshi = 70 Satoshi
node B has 35 satoshi


Probably your node even takes some routing fee which could have a standard value of at least one satoshi in that case your final balance would look like this


  (A)--35sat------25sat--(you)--46sat------34sat--(B)


meaning: 


node A has 35 satoshi
your node has 25 satoshi + 46 satoshi = 71 Satoshi
node B has 34 satoshi