I unfortunately over contributed to my Roth IRA this year. I'm planning on withdrawing the excess contribution before the tax deadline this year. I know that if you make money on the excess you end up paying tax on it. My question is that if you lose money on the excess contribution, can you claim that as a loss?

I think the answer is in effect 'yes'. Looks like you reduce the amount of excess contribution you withdraw by the loss you had.
Look at pg 51 in the IRS's Publication 590:

Publication 590