Drop of performance after https

Hi best Support Team ever,

I am really desperate since our musikzentrale.net website experienced a dramatic drop in THE HUB performance points, from 84 to 59 by now. I am still using WP Rocket as caching and performance plugin, but maybe my site could do so much better when using only plugins from a single company?

Anyway, could you please assist me in getting back to our pretty good shape before the switch to SSL? Thanks in advance,

cheers, Sebastian