As you mentioned that your concentration level went down after 19. It’s not concentration level went down, but you started focusing on more of practical and philosophical reasons of things. for exmaple, Concentration means 2+2=4 and just understand it…. but your tendency would have been like why + sign was meant for addition and how 2+2 resulted in 4; probably by simulation of adding 1 as many times as value which is at the right side of + sign.
Instead of focusing on outcome of a process you must have been focusing on the process. People expect the outcome and not the reasoning behind it. YOu must be focusing on introduction part of the chapter than the rest of the chapter…….
I don’t think there is anything is wrong with your concentration. Better you get in the higher studies related to simulation of things that cover whole flow of execution. Like understanding of water pump as a whole and how it simulates to pump water not just how to operate the pump.
Put on only Yellow sapphire. Your lagna lord is Saturn, it would constraint you to express in the work field which is good in one sense. Though you might be expressive in home but not outside world. If you put on perl it might enhance your emotional part that might lead to being too cautious being expressive.
Your job and leadership skills would surface between 27-33.
Only yellow sapphire I would suggest.