It is possible that the USD+ token price experienced a significant drop since you deposited the 300 USDC into the vault. This could explain why you only received 200 USDC when you withdrew. Additionally, it is possible that the USD+ strategy had an exploit at their Avax side, which lead to the negative rebase of the USD+ amount. This could also explain why you only received 200 USDC instead of the 300 USDC you deposited. To make sure, you should check the USD+ token price to see if it has dropped significantly since you deposited the 300 USDC. If it has, then that could explain the difference in the amount you received. You should also investigate the exploit at the Avax side to make sure it did not contribute to the difference in the amount you received.