Mildew on Black Medick

Yesterday I noticed that a lot of the Black Medick Medicago lupulina growing in the gaps in the patio was looking very unhealthy. I looked closer and saw that most of it was infected with a mildew on both the upper and the lower surfaces of the leaves. I’ve never noticed this mildew before despite the medick being literally right on my doorstep, so I wonder if the excessive heat weakened the plants making them more susceptible to mildew. Anyway, I was wondering if anyone would be able to let me know which species this might be, or narrow it down a bit?

Thank you

James