riot is up to something ( helpz ))

so i recently did my placement matches on my plat 5 last season and went 6-4 and got into silver 2 i was a little upset but at the same time understandable since it had gold 3 mmr last season, but this time i got on my other plat 4 account which had completely normal mmr maybe even higher i went 5-5 and got silver 1. This happened to a mutual friend as well.He was plat last season and got placed in silver 1. This never happened last season cause i specifically remember getting placed in gold 3 after winning like 3 out of 10 placement matches when it was plat s4 LOL sorry for the really long paragraph but any idea whats up ?!?