If all the strats were opening at the same time that would be more of a concern.  It would show that there is not enough diversification between the strats.  That they have similar settings and indicators.

As for selecting the top EAs.  There are several ways and Petko has some very good videos explaining them in detail.

You can run all the strats on demo for a certain time (1 week, 2 weeks etc) and then choose the best performers.

You can wait till a strat has a certain amount of trades with a good PF ratio. (Say min of 5 trades with a PF greater then 1.2)

You can hold  back 1 month of data when creating all your strats.  Then feed them back into the validator. Change the data to the last month and then run them forward.  This will simulate how they would have traded in the last month.  Then use the filtering option to say choose the top 10 / 5/ 3 or whatever.  And then transfer these to the “Live” account.  This is my preferred method but you will have to test for yourself and see what works for you…