Today was a down day for the S&P/ASX 200 (INDEXASX: ^AXJO) (ASX: XJO), which lost 0.6% to 5111 points. The axe fell extra heavily on some companies, which are detailed below:

Fortescue Metals Group Limited (ASX: FMG) fell 7% to $2.87 after trading as high as $3.25 early this morning and closing above $3 yesterday. Initially driving the rise was an 18% increase in the value of iron ore overnight, although shares began to fall after the company announced a memorandum of understanding with Vale SA, which might buy up to 15% of Fortescue’s issued shares on-market.

Despite today’s fall, Fortescue shares are still up 43% for the week, and 33% in the past 12 months.

Bellamy’s Australia Ltd (ASX: BAL) dropped 4% to $9.86 on no news today, complemented by a fall from smaller competitor A2 Milk Company Ltd (Australia) (ASX: A2M), which lost 6% to $1.56. Both Bellamy’s and A2 have experienced a strong run in their share prices over the past 12 months, which at times have reached levels that might challenge conventional valuations. Potential investors are counting on an explosion of consumer demand in China, which would be a long-term tailwind for both stocks.

Despite pulling back significantly from recent highs, Bellamy’s shares are still up 264% in the past 12 months.

Slater & Gordon Limited (ASX: SGH) lost 6% to $0.365 today as ongoing investor uncertainty about the company’s operations and financials continues to batter the share price. Indeed, the company’s ongoing restructure and talks with lenders has even lead some to question whether the company could be going broke, a question which is difficult to answer. Other listed law firm, Shine Corporate Ltd (ASX: SHJ) made headlines recently when shares crashed after management announced issues with its Work-In-Progress (WIP) accounting. Shine shares also fell 4% today.

Slater & Gordon Limited has lost 95% of its value in the past 12 months.

Adacel Technologies Limited (ASX: ADA) shed 5% to $1.98 as the market pares back expectations for the stock, which delivered a very successful half-yearly report in January. However, the fact that shares fell after posting a 40% leap in revenue and a 606% increase in profit implies that the stock has a significant amount of growth already factored into it. Management has stated that they believe the current strong momentum will continue for the remainder of 2016, and that guidance of a 70% increase in profit before tax should be achievable.

Adacel shares are up 434% in the past 12 months.

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Motley Fool contributor Sean O'Neill owns shares of A2 Milk. Unless otherwise noted, the author does not have a position in any stocks mentioned by the author in the comments below. The Motley Fool Australia owns shares of Bellamy's Australia. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.