The reason for that is most likely that there was nothing Feldman thought her could do with that evidence, so he simply left it alone. Which is the best thing to do.
Remember, the defense doesn't need to prove their client is innocent; it only needs to raise a reasonable doubt about the client's guilt.
In the course of doing so, you contravert or call into question every item of evidence that you reasonably can, but you also keep in mind that everything you touch, you effectively put a spotlight on. That's good if you can do somthing with it; but it's bad if you can't. Very bad. It makes your case look weaker.
How Feldman "dealt with" the DNA evidence was by ignoring it and countering it the bug evidence. That, imo, was a good tactic.
Again, his goal is to create doubt in the minds of the jurors. I think he did a respectable job of attempting to do that.
One more thing to keep in mind here, is that -- unlike the prosecution -- the defense has limited resources to draw upon. It needs to spend its money efficiently. It can't hire every expert in the world in order to try to counter everything. In this case, hiring bug experts looks like it was a better strategy than hiring DNA experts would have been. We'll see,
The DNA evidence, on its own, even if damning, is (probably) not sufficient to establish guilt in the mind of a reasonable person. Not in the presence of other evidence that is exculpatory.