Edexcel economics am I cooked?

Hey guys I used a unique analysis in one of my Econ papers essays and I wanted to check if I’m cooked. Basically I said for a supplier to a monopsony a monopsony pushes down prices for firms due to its market power, as there is effectively only one buyer and many supplying firms.

However, I then drew a cost/revenue diagram for an individual supplier and shifted the AR and MR curves inwards, to show a fall in revenue for firms across all levels of output as prices are pushed down. Some sources say this is correct as monopsonies determine market price so push down prices for all firms whilst  others say I should instead have shown a movement along the curve. My teacher says it’s a decent point but other say it’s a bit dodgy. Thoughts?