As Wolf359 points out, losing 1/3 of your yield is no joke. So, it is great that you are thinking about solving the expense issue...that is the first step! Best of luck.
Here is one way to think about this.
1. Stop putting more money into your current bond funds, esp the two most expensive.
2. Start putting the money in your new bond funds....you may also want to take a peek at VWITX.
If you do not have new capital, you can stop dividend reinvesting and put the dividend money into the new funds.
3. Take the two highest expense ratio funds and slowly sell small amounts (keep taxable income low) and move it to the Vanguard funds. This will keep your tax load low.
Make sure you keep the tax slab in mind too....if you are $10000 below the next tax slab, then you can sell enough to realize $10000 worth of gains....ofcourse, you
have to pay the tax man some...
4. Another optimization you can do is to keep the lowest capital gains funds...once interest rates start rising, bond funds will fall, and then you can play the tax loss
harvesting game...sell one fund for a gain, one fund for a loss and balance it out.
NOTE:
Consider VCADX which I use. The current price is $11.82 appx. This is almost close to the highest price in the last few years.
Even if I had a chunk of money, it would probably be better to slowly dollar cost average into this fund. Else, I may be holding a loss for a couple years.
So, it makes sense to slowly DCA anyways....so, I would move off the Fidelity funds to Vanguard funds slowly.
And, I have seen appx 50-60 Vanguard funds and I have not seen a Vanguard fund with a front load option i.e. no fee upfront. Ask your Fidelity rep what funds he was talking about...maybe it is just a pressure tactic to keep you in Fidelity.