Hello Aspirant,

After reading your query, All I can say is, this is not a huge concern to worry about. The most important thing required to crack JEE is practice and having clear concepts. Forgetting concepts can be minimised by solving conceptual questions on a regular basis. Keep taking Mock Tests to improve your confidence. Never get disappointed for getting low scores in practice test. It happens because there might be few topics which are difficult for you to solve. Similarly, Few could be easy.

Keep Working on the topics where you lost your marks and make sure you don't repeat them again.

All the Best...

Hope this helps...