There is no reason for this dump, I think the traders are trying to cash out their profit, and just waiting for another moment to get in again. You know that a lot of the red candle in every altcoin(included bitcoin too) It looks just a usual thing in crypto. If you already pumped and it will be significantly dumped as fast as possible. Don't worry about that. If you can buy them at the right price and you will be able to gain a lot of profit in the future.
This is just the matter of time until all of the cryptos get pump again.