You can see what your at the wall draw is for about $20 if you're interested in it. There are a lot of people around here that try to get away with ignoring suggested minimum wattages, I guess that's fine, although when things stop working I prefer to make sure I'm not ignoring what the engineers have asked of me, since what things should do and what they actually do are usually not the same.

That said, I would still like to know if the cards are the exact same model, of if you're CFXing cards from different manufactures or different models. You can grab any 2 reference cards and use them together, but if you use an aftermarket card, it's best that they are identical. Since your build doesn't have 2 and you didn't say it was the same, I don't want to make the assumption that they are.

Since I didn't explicitly explain my comment to the person who made a napkin math assesment of power draw, I'll do it here in the hopes people are paying attention to my concerns about the PSU. In the source previously shown (here) you can see that draw at idle makes a pretty big jump from 1080p to triple monitors. That makes me feel like rendering 1440p frames on your monitor is consuming a lot of power. Can you try setting your resolution to 1080p and doing a 1080p benchmark or two and see what happens? The power draw at 1080p may be fine for your PSU, but I think it's too much at 1440p. Also, do you have a separate set of wires going to each plug individually or are you sharing connections from a single wire? You should have 4 cables going from your PSU to each of the 4 total connections on your two cards.