Temp guns cannot test the temp of water. It will read the bottom and with distortion. There is not a great way the easiest is to check against a know accurate thermometer (don't you have a herpstat ? or am I confusing you with some one else?) herpstats have very accurate probes they are spec'd to 0.9º+/- but I have a platinum RTD and 19 probes connected to herpstats and the worst of the lot is actually 0.7ºF high. If you have a herp stat you can use that to check the thermometers. Remember the IR gun should be directed to a target of brown paper for the best accuracy.
If you don't I use the rule of averages and check 3 at least and preferably more (I buy lots of 20 super cheap ones and toss the incorrect units I usually get about 17 good ones. I would guess that the correct temp is close to 93-93.5º the other two would be incorrect try checking something opaque and see if the two correct ones are now reading closer to the IR gun. They are great quick tools but can be very easily fouled and be very incorrect (shiny things especially, water.)
Or you be driven mad by the junk sold on the market and how far off it is and decide to invest in a traceable high accuracy thermometer, no wait that was me!