I had thrips and although annoying they don't do any real damage to plants. I ended up getting rid of them by spraying with a nicotine solution every 4 days for a couple of weeks. the eggs are laying in the soil and can stay dormant for weeks before hatching. so you need to be ready to spray whenever you see just one thrip - cos for every one you see there's probably like 30 on the plant. eventually you will lower the numbers enough that their life cycle is broken.

with regard to your blotchy leaves thats almost definately a nutrient issue, have a look at these links and see which picture/description best fits.

http://www.drugs-forum.com/growfaq/1382.htm
http://www.drugs-forum.com/growfaq/804.htm
http://www.drugs-forum.com/growfaq/951.htm