fruit, if he is meeting his milestones, and is happy, producing wet nappies and you are not at all concerned about his weight gain (ie not noticed reduction in apetite etc) then he has probably just peetered out to his natural weight. But, maybe go back a couple of time over say a 6wk period, and see that he continues on that 25 centile, maybe that would reassure you? Many babies drop lots of centiles from birth, or go up several, as birthweight is not really an indicator of future weight/height. In a way, the use of the centiles is not a useful tool, as it is mostly all the HV does to assess how a baby is going, and failure to gain weight, or excessive weight gain causes unnecessary worry as so much emphasis is put on it, when it is only one measure of how well a baby is developing, and not always an accurate one at that. DD plummetted the charts, caused all sorts of worry and she was just finding her place weight wise. She has just moved in to 3-4 clothes at almost 4, and is taller than some, and shorter than some of her friends of the same age. She weighed 21lb at 19 months. A friend of mine, her baby was on 75th centile. Now she is off the charts. But friend was diabetic so likely to produce heavy baby. Her girl is tiny, she is 17lb at 19months! But perfectly healthy and bright.
I hope he is ok, and understand your worry. It is a shock to see them going downwards, and for you, so suddenly. We went straight to see our gp when we had concerns raised, as we did not feel our HV knew enough (or thought she knew too much) to give us the answers we needed. GP was fab and really reassuring.