For those interested in A3s (all of them) dropping hashrate at the same time, in all pools, there is a channel discussing that in the unofficial sia discord (https://discord.gg/EVn3HPK). So far the theory is that is caused by some blocks, probably a bug in the A3s. The issue lasts until a block is found and they go back to normal. Boards restart when mining these problematic blocks and fans stay at 100% after that... Very weird.