Should I get M2 Freeze on the sale or rank up a bit and save up for M2 isida and M2 hornet? PS: I'm WO5 and atm I have M1 isida, M1 hornet and M0 Freeze

You probably have had tons of these complaints and I might be annoying, but please try to help me out. I recently (couple of weeks ago) started playing Tankionline and I was having fun the first two weeks. Then all of a sudden the game started lagging big time and FPS dropped to around 5-20. It isn't a connection or internet problem. I also changed to minimum graphics and deleted data from flashplayer and maximized the information storing from settings, but even then nothing changes. As it happened overnight then may it be some update's problem or is anyone else having the issue? I'd really like to enjoy my gameplay...