Lower infill results in bad prints

I recently built a Prusa i3 and so far I've found some fairly good results with the following settings (using Slic3r):

3mm PLA

195 C

Retraction: 1.5mm

Lift Z: 0

Fill Density 70%

Pattern: Honecomb

Layer Height .25mm

Vertical Shells: 4

5 top and bottom solid layers

When I print with the above settings they come out looking pretty good, like so:

[imgur.com]

(Ignore the backwards text. I have since fixed that)

Anyways, I've used the above settings and lowered the fill density to 25% and 12% since I've read that most people don't go above 50% and I've seen pretty much everyone does around 10-25%. This is how they've come out:

[imgur.com]


They look terrible.

I've tried every setting I can find, and they continue to look bad.
Is there something insanely obvious I'm missing? I have no idea what else to change to get these to look better.

My hunch is that there isn't enough time for the previous layer to cool before the next one is printed. Are you cooling the print directly?

If not, try cutting down the speed of the printer and see if that helps.