In general you wont get a true evaluation of a beer until it has been critiqued multiple times. And to be certified in the BJCP you don't need to do a ton. National and beyond is where you start to see the most informed opinions in my opinion. That being said:
Do you know how your entry was stored for each competition? Are you certain that your bottling practice was consistent for each bottle? Are you sure some contaminant didnt make it into a bottle? Where were you beers placed in the flight?
Judging is very subjective even with guidelines and you will see that the scale for what is "fair" ,"good" or "excellent" vary along the way. For instance the BJCP says that a "Good" beer is in the range of 21-29. If I give a beer a score in that range it has an obvious flaw or is mis entered. It would be a beer I likely couldn't have a second pint of. To me a 35 is a good beer that may not medal but is solid and 40+ are you medal worthy beers.
I am a certified judge that has the points to be national but can't be bothered to take the test. I competed heavily before going pro and still compete now when I can. I love it and it has made me a better brewer. I learned that you have to take everything with a grain of salt. You need to realize that when you got to second round it becomes completely subjective. Just this past week I got my highest score ever and one of my lowest. An Alt I entered was judged as having a sour and vegetal note. The beer was excellent toll it kicked in the keg, but something obviously went tits up in the packaging process. Maybe a fruit fly, or a dirty bottle, or maybe they mis sorted bottles I'll never know. It's part of the game and you either love it or hate it but I don't think the BJCP itself is flawed.
The competition circuit made me a significantly better brewer without a doubt.
This. +100. All of it.
There are a lot of factors and definitely a lot of crummy judges. The bar to pass the exam for recognized is quite low (it's actually very hard to fail if any effort at all is put in), and with moderate preparation certified rank is easily obtainable (and I say that as an exam grader).
The bar to make National rank is *far* higher, and the bar to make Master is astronomical.
Of course I've seen recognized and certified judges write better, and more accurate sheets than some national judges (many of whom after doing it a long time just get lazy).
However, as said it's entirely possible that the judges were objectively accurate and there was something else going on. While a little variation is normal (which is why mini-BOS, and BOS itself, are things) a swing that wide could be bottle variation on your part, or contamination, or mishandling (on your or the comps part), or flight order, or flight length, or something about the judging setting.
However, the sheets from any level of BJCP judge to tend, on average, to be better than non-BJCP judges (except maybe Cicerones). I actually find non-BJCP pros to make the worst judges.
It's part of the game. And it applies to call comps, BJCP or otherwise. If you don't like it, don't enter.