Forgot to ask, should I cut the diseased fronds off? Or would the palm benefit for me to leave them on to get new growth faster?

Phoenix palms very commonly get spots during cool and damp winters. I assume you got your palm from central Florida? They have had a particularly dreadful winter. Leave the fronds on and provide a dry and warm place to promote new, clean growth.

Keep the soil moist but the leafs dry and spray with a fungicide.

I had once received a P. canariensis out of South Florida, it was covered in ugly black spots. I kept the plant and eventually new growth reverted to normal. I attributed to the Phoenix clan's intolerance of S. Florida's humidity. I wouldn't worry about the health of the palm but it's up to you if you want a refund or alternate course of action.

CenFla's winter has been cool but very dry as typical. However I doubt 30 degrees would hurt that palm.

I am in the Orlando area, and have a 14" Phoenix dactylifera that has similar spots. It seems to be growing okay though.

I have the urge to cut the diseased fronds off, but I also know that Phoenix grow slowly. I just hope the spots don't transfer to the new growth.

I am familiar with a crop of these in 3g containers. I would be hard pressed to find ONE that doesn't have fungal spots on the lower or even all leafs. Since this problem occurs all year for me I attribute it to the overhead irrigation and the fact that they are arranged pot tight. It's my experience that when they are bumped up to larger containers (or out to a field planting) and spaced more apart that they grow out of it. To prevent the problem from becoming worse with your plant, do some preventative fungicide spray and as well pour some peroxide into the growing area. This should keep the problem from spreading to the uneffected fronds. At this point don't trim the fronds. Even though they are unnatractive they are still providing for the plant. I'm confident that yours will grow out of this.

Thank you for the comforting advice. I'm glad to hear I'm not one of a few with this problem, but rather one of a majority? Either way, I will spray with fungicide and hope it doesn't spread to my other palms.