Seems like somebody sent about 50 MH/s and then dropped the hashrate. That caused increase in difficulty and longer time to find the block as the hashrate was low and diff was high. This had to be fixed in our last hardfork where LWMA algo was implemented to prevent this (see https://pluracoin.org/hardfork1 and https://github.com/zawy12/difficulty-algorithms/issues/23). It was working fine for last several months but it seems like it's time to review the implementation and readjust LWMA settings again