Using credit builder credit cards to improve credit file

Hairymonster

Got Noddle improve to try & work on my credit file & see where I am at, and also see what the jump may be like(if any) when BR falls off in next months report- it's sitting between poor and very poor at the moment.

my credit score has went down the past 3 months from August it's went 572, 551, 548 & this morning 533 which is the lowest since June when I thought it would have been going up. I have been gradually increasing the amounts I have been taking each month on the credit cards; basically anything I can buy with a card i'm using these credit builders- but over 2 cards I have £250 & £500 limits but although I am using a lot I am always paying them off fully as I thought this would increase my credit score? I've been clearing varying amounts from £150-£600 each month which is fairly easy to do as after all bills I have about £1400 each month spare- so I pay fully then use throughout the month again.

I was hoping my score would start going up because of this but appears to be going down- why is this? I have had the cards for 5 months.... do they need to go down before they go up? i.e do they need to see that I can continually pay each month the full balance?

Is there an optimum % of the card limit to use when rebuilding credit file? i.e maybe 50% of the limit of each card? less than this?

In Noddle; under what's impacting your score?

it says: "The total balances on your lending have increased over the last few months"