Puzzle solving skill is falling down

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weareneveralone

I have seen that my puzzle solving skills is falling down. Specially after solving 10 to 15 puzzles correctly I take more time to solve the new one whereas before under such circumstances my precision used to go high and high. But nowadays I am truly facing problems. I need more time to sense the puzzle. Is it due to eye problem and therefore less neuro response or due to any mental stress? What do you think? What might be the reasons of such strange things? I can remember that with my old Chess.Com account, after joining I could solve at least 30-40 puzzles correctly, each within few seconds. But nowadays I fail, I need comparatively more time. I need other player's opinion.

weareneveralone

Please take example of the following. Average time is 0.18 seconds whereas after solving many puzzles at a time I stuck to this one and took 0.56 seconds to solve. Why such strange things happens?