@JSa2c24 I believe @Penn95 and I have differing opinions on the subject.
First off, Prepscholar is a secondary source - they are making their interpretations on the primary source (which is Penn’s}.
Penn says:
http://www.admissions.upenn.edu/apply/whatpennlooksfor/testing
Having said that, since you “took the test but didn’t score so hot,” there may be other weaknesses in your application. So while not submitting Subject Tests may not hurt per se, the lack of them may bring something else to light that will hurt, IMO. But we’re mot AO’s, so all you can do is submit the best package you can and then wait. Good luck.