i only put the rent up four times in all that time but if they get the idea that they can get compensation they will do it i am sure
It won't go back as far as 2013, no.
Still, if the Deposit was valued at £1,300 you could be in for a hard time. Obviously however frequently you put the rent up isn't relevant to this situation.
All that's relevant was whether you protected the Deposit... and you didn't. Hopefully they aren't aware, and don't have a chat with an old chum down the pub who makes them aware... then, as each year passes your exposure becomes less.