Swampdonkey has step 1 covered. Cleaning and then treating your line is the first thing I'd do too. Question: How did it perform the first 2 times out?
Shy of looking at a line that's better suited for warmer temps that's going to be your best bet. I know it's been hot here in PA for a while, but unless you can get mileage beyond warm temps with a different line, I'd probably hold off on a tropical line. However, a line like an SA Textured line or Ridge Line from Airflo might do a little better since there would be less surface touching the guides.
This thread might be worth a read:
Tropical Lines Question