the card on the mining can work for days, and then it produces this,

[2018-06-28 23:25:12.770] ADDENDUM APPLIED: 1075187 --> 1075188  10 blocks added
[2018-06-28 23:25:12.770] Stratum detected new block
[2018-06-28 23:25:12.926] thread 0: 3670016 hashes, 2080.37 kh/s
[2018-06-28 23:25:12.926] Thread 0 is going to scan with start nonce=00000000, end_nonce=07700000
[2018-06-28 23:25:12.926] [GPU2] scratchpad update 42408484
[2018-06-28 23:25:35.417] ADDENDUM APPLIED: 1075188 --> 1075189  10 blocks added
[2018-06-28 23:25:35.417] Stratum detected new block
[2018-06-28 23:25:56.428] ADDENDUM APPLIED: 1075189 --> 1075190  10 blocks added
[2018-06-28 23:25:56.428] Stratum detected new block
[2018-06-28 23:28:25.339] ADDENDUM APPLIED: 1075190 --> 1075191  9 blocks added
[2018-06-28 23:28:25.339] Stratum detected new block
[2018-06-28 23:28:51.764] ADDENDUM APPLIED: 1075191 --> 1075192  10 blocks added
[2018-06-28 23:28:51.764] Stratum detected new block
[2018-06-28 23:31:02.175] ADDENDUM APPLIED: 1075192 --> 1075193  10 blocks added
[2018-06-28 23:31:02.175] Stratum detected new block
[2018-06-28 23:31:59.736] ADDENDUM APPLIED: 1075193 --> 1075194  10 blocks added
[2018-06-28 23:31:59.736] Stratum detected new block
[2018-06-28 23:32:41.904] ADDENDUM APPLIED: 1075194 --> 1075195  10 blocks added

and the speed on the pool drops.

because of what is this and how to deal with it?