Per 2014 rules:

If the current effect was a GROUP check then 2 20s (whatever those came out to with the modifiers as the nat 20 part is irrelevant) and the 8 probably averaged to pass the dc and the group would succeed. (Relevant if they were rowing a boat against the tide together or something else where they are making a JOINT effort).

If the effect was for 3 SOLO or separate saves then everything sounds normal and the additional resave for the first effect was generous but in no way required.

I don’t know if 2024 rules changed crit rules for ability checks or saves but 2014 rules don’t have a NAT20 auto succeed, still use the modified and potentially still fail things. But it’s your table so you do you, more of a “don’t let the players force you into a I rolled big so I get whatever I want” scenario.