well, IMO this happens to everyone, I dont know if that pronouced in higher belts as in blue becuase, well im just a blue, but here is my take on the subject...
while its true that we all plateau once every x amount of time, and nothing seems to be going right, and nothing seems to work, its depressing, after a while, one day, everything clips and you make a big jump in progression, is like, o shit im kicking ass again! well, what happened is that you have been working a lot on different things, because things that used to work well, are not doing it anymore, then you started to look for solutions, and after a while, you are able to implement those solutions. For example, I used to triangle people left and right (white and new blues) in the gym after a while, I wasnt hitting as much triangles as I used to, later on I wouldnt hit 1 in class, that wouldve been unacceptable for me back in my triangles day, what happened? I stopped paying that much attention to the triangles, was working on arm drags and back attacks, when one day I said, ok time to go for triangles again, I was getting a freaking hard time getting them on people I used to triangle at will.. what happend? did my technique went to hell? nop, my class mates evolved, they learned how to counter it (the old set ups), so I had to start working on new set ups, I did find some more success, but not the same I was having before? why? well, white belts that used to be total noobs were not that noobs anymore, and the rest just kept progressing, learned what not to do, where NOT to place their arms and where NOT let me place my legs... White belts evolve pretty fast up to one point, blue belts get stuck a lot to turn to purple, that means that your progress will be slower as you get more training time, unless you are constantly working on new things and constantly drilling all those new things. With some strong basics, seasoned white belt should be able to defend pretty well (this means not get tap 5 times in 5 minutes) by a good blue, still he would get owned by most blues (im talking in general, of course there are white killers and the skill level differs a lot from school to school)... so you would think that its solely your fault that you are not tapping left and right guys who you used to tap a while ago, when in reality, its a mix of the 2, him getting better and you not getting better as fast as he is... remember this, you are not the only one training, and you are not the only one who will progress with training...
dont worry, it will pass, what I do when I get in times like this? work on some new stuff and always, always try to have fun...