I'm gonna throw this out there: Do you know absolutely, and 100% for sure, that your safe-light and it's position is really safe?
Consistently muddy or hard to deal with prints usually points to a process issue - even if the negatives are not the most perfect negatives. You'll begin to feel that something isn't quite right - and it's at that point you should verify process and not necessarily materials.
Also, 5 seconds is way too short for a print unless you're barely enlarging or contact printing. Don't enlarge wide-open either.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.