I wouldn't use any more trichlor in your pool since your CYA is 50. That is a good level and trichlor will cause your CYA level to go higher which you don't want. It is also very acidic which is why your pH is dropping. Stick with bleach. In a 35K pool, each quart of 6% bleach will raise your chlorine level by about 0.4. With a CYA of 50, you'll want to try and shock the pool up to about 15ppm and try and hold it there until you can go from sundown one evening til sunup the next morning without losing more than 1pm of chlorine. Since this is such a large volume pool, if you have access to some 12% hypochlorite, you can use it instead of bleach (which is 6% sodium hypochlorite). Test 2-3 times per day and each time, add enough chlorine to take it back up to 15. There is no such thing as testing and dosing too often while you are trying to clear a pool. The more often you do so, the faster you can get it cleared up. Keep an eye on your pH and make sure it stays above 7.0. As Ben said above, don't add any other things. Some pool stores will try and sell you numerous products that "will fix the problem" but in actuality, will just make it worse. Keep us posted how it is going.