I just charted your DD on the WHO charts.
With the weights you provided:
9 months: 16 pounds 4 oz = 7.37 kg - on the 15th percentile
10 months: 16 pounds 10 oz = 7.54 kg - on the 15th percentile
12 months: 16 pounds 14 oz = 7.69 oz - just below 15th percentile (less than 100 grams below)
Honestly, this "dip" is so tiny it may just be a case of your DD having a full bladder/bowel at the time, versus just having eliminated the earlier time.
However, it is totally normally that children drop a bit on the charts, at various times (different times from child to child, so not necessarily following the percentile!) once the child gets more mobile, around 8 months - 2 years. Usually, according to the dr we saw (very mainstream), they catch up over time, and she recommended that we weigh DD in about 1-3 months if WE were worried (she wasn't).
DD was tiny all along, below 3rd percentile for most of her first year. Her "dip" happened around 18-20 months (by which time she was up close to the 15th percentile) , she even lost a little bit of weight. She gained it back and is now in the middle between 15th and 50th percentile.
Someone asked about my son's growth. He's going to turn 4 in December, and weighs 33 pounds naked. He's about 38.5 inches tall. According the charts the doc uses, he's about 10th for weight, 25th height. (And 90-something head, lol, just like his daddy). My husband had the exact same growth. In fact, Harrison was 1 pound heavier than my husband was at 9 months and my husband was formula fed. I don't worry about my son. He eats pretty well, and he's pretty comparably sized to his preschool classmates (even those older than him). He can wear 3t and 4T shirts, but is 3T in pants. Other than people constantly mistaking him for a girl because he's pretty and has long, shaggy hair, he's good.
Also, my husband is about 5' 9" now. He was short and skinny in elementary school. This smallness is just not surprising. Also, my brother and sister were always extremely skinny, to the point where they had tests run to make sure it was nothing serious. It wasn't. Just skinniness. Believe me, with age the metabolism slows down!
As for solids, we're plugging along. She eats a bit....tonight she was picking up each lentil and was putting in her mouth but I'm unsure how many she actually ingested. She LOVES playing in food though, she was an absolute mess tonight. She also really enjoys rich tastes, like Alfredo sauce and mashed potatoes. Goat cheese. She's definitely attempting to put more and more foods in her mouth, like Cheerios, bits of crumbled tater tot....anything we are eating. We had our first OT visit the other day and the OT seemed a bit unclear about why her services were necessary. And given that I have done/am doing basically EVERYTHING she suggested, I have to agree.