Its nice to hear that someone else has also experienced the same problems at Rawal lake as i did.
Actually what you are calling a chemical is not chemical really. its a combination of a number of herbs/additives cooked/mixed together and as for its formula, i feel its easier to design a aircraft engine. it has a strong smell and there is nothing else wrong about it. The reason that you are not getting the fish is because if the fish is getting a bait that smelly in the area than it wont come for something like atta/haldi. Secondly i feel haldi and vanila essence dont go together as they have very different smells. Recommend using one of the two.
As for the charai, there is every thing wrong about it because, as you mentioned, it contains a herb which seriously effects the digestive system of the fish. Many of them, specially small ones, can not recover and either die or their growth is seriously retarded. I have been talking to the people about not using it but in vain. Many of them have no idea of ethical angling, conservation etc. May like to do the following
1 Dont sit at the place where the lake has been extensively ground baited with charai. Select a new spot for yourself, may be on the farther side of the lake (Bani Gala or recreational park side).
2 You must not use the harmful herbs, but ground baiting is essential.
3. Must carry the earth worms. Carps, specailly Gulfam can be caught on them. Today morning my son caught a gulfaam and a grass carp with earth worms.
4. Dont be disheartened. keep using new techniques. After initial failures, now i have started having some success. Good luck.