Hi, I am hoping someone can help with a question about formula please. I've just started using formula for my 5 month old daughter and every time I make up a bottle it seems to have a few 'lumps' of undissolved formula in it which get stuck in the teat hole and block it up. Does anyone have any tips for mixing up a bottle to avoid the lumps? At the moment I'm storing the bottles in the fridge three quarters filled with boiled water, then I add hot boiling water to warm it a little, then formula, then shake. I'm using both Avent and Tommee Tippee (closer to nature) bottles and it's happening with both of them. Also the anti-colic valve gets clogged on the Tommee Tippee ones...any help would be great!