19:01:06:633 12f4 ETH - Total Speed: 77.502 Mh/s, Total Shares: 2, Rejected: 0, Time: 00:03
19:01:06:634 12f4 ETH: GPU0 28.916 Mh/s, GPU1 28.978 Mh/s, GPU2 19.607 Mh/s
19:01:06:848 1d4c GPU0 t=76C fan=45%, GPU1 t=76C fan=54%, GPU2 t=73C fan=31%
76C seems a little warm for start up. What OC do you have these set to? How about undervolting?
Turn the rig off, leave it off for 2 minutes. Turn it on. See if that helps. If it doesn't set the cards in question (that are not working) back to default speeds and see if that works, then OC slowly from there.