Can I choose to refinance only some of my loans even if they are from the same lender?

I am looking for guidance on what to do about paying back my student loans. Unfortunately I work in the Human Services field and have not been able to afford to make significant payments on my loans since graduating but I feel like I am finally in a place financially to start making some progress. In what I have read so far I know that I should pay down my loans with the largest interest rates so I would focus on the 6.8’s and specifically the 3,500 loan first. I currently make payments of $331/month to the lender for all 4 loans, which I know basically covers interest and minimal principle. I think I can make an additional $150/month just on that particular loan to speed up the payments and once that is done roll that amount to the next loan. However, I have also started thinking about refinancing through Citizen bank of Sofi but I haven’t contacted them yet in person (just did online quotes) because I have also read that it may not be in my best interest to refinance this late in the payment game as I have been paying for a over 7 years and I want to know what to ask for before I call. On a side note, I may also qualify for the student loan forgiveness program but wouldn’t be considered officially until it rolls out in 2017. I also read there is no guarantee once found eligible that they congress will uphold the program in 2017. I have no worries about the 0.33% loan and have been making payments of $250 and should have it paid off by summer 2016. I think the only way I would try to refinance is if I can choose to refinance the 6.8% loans. I have excellent credit but I do not want to take a chance with a low varied rate that may change and would rather a fixed rate that’s a little higher. I’ve seen quotes for 4.5%. Does anyone have any suggestions?

I currently have 4 loans through one lender:
1. $6,000 @2.33%
2. $8,500 @2.33%
3. $7,500 @6.8%
4. $3,500 @6.8%

And 1 loan through another lender
1. $4,500 @0.33%