I had the same situation.
I started out with a loud clatter, but no obviously loose rockers and one easy-to-compress ball stud. I did Herr Fuch's finger check and found four with problems. Replaced all ball studs and all worn pads. The clatter went away, and I ended up with several 'tickers.' Did the adjustment with the guage, replacing four 5.1's with 5.45's. Now I think the valves are quiet, but I have some chain noise.
IMHO, you really can't tell from bench testing whether you will get noise when the engine is running. If you have noise, and you cannot find a clear indication of the problem, then I would do all the ball studs, check the condition of the pads, and check the preload with the guage and adjust as needed.
In your case, I would try replacing the two you found collapsed, check all pads for wear, and do the preload check with the guage.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe