They have been mating regularly (many many times per day) for about 3 weeks now, and so the foam test isn't particularly helpful - they both express foam, but if they're mating regularly, that could possibly why.
A few weeks ago, I purchased a pair of Japanese Quail from a local breeder.
I've had them for around 5 weeks now (And they were 9 weeks old when I purchased them).
I've been feeding them chick starter mixed with budgie feed - that's what the stockfeed store suggested - as game bird feed isn't...