low red blood cell count/low platelet count--NO OTHER SYMPTOMS

Hi,  
   I have a seven and a half year old black lab/rottweiler mix, he has always been healthy.  In Jan of this year, we had a routine CBC done because he was getting older--no other reason.  His test results came back normal, but his platelet levels were low but not to the point of severe concern.  The vet wanted to retest each month--some of the time the counts needed to be redone because his blood was clumped.  All showed that his platelet count was on the rise.  Throughout this a coagulation profile was also done.  The vet decided to, I believe in March, test for a tick borne disease---we chose not to test because he is on Frontline Plus year round and should therefore, not have been infected with a tick, the vet put him on a cycle of doxycycline and there were no major changes in his platelet count.  The beginning of May, the vet consulted with the lab doing the blood work and decided to do a final CBC and if his platelet count was still a little low he would just diagnosis Fine Lee with Thrombocytopenia (his platelet count has never been in the critical range).  The results came back that the platelet count was normal (this has never happened in the 5 months that we have been testing) but his red blood cell count was at 5.6, I believe that when he had his last CBC his RBC was 8.1, I believe the last time he had a CBC done was in Feb), because Fine Lee's blood was clumped during this test, he decided to take blood again, he went last night and I am awaiting the results.  Throughout this entire process my dog has had not symptoms of anything being wrong, his appetite has not changed nor has his activity level or water intake.  Any suggestions on where we should go from here?
Any advice/guidance would be appreciated!!