Final question about my lawn

Sorry to labour the point but the other thread petered out without answering my main question but thanks for responding.

I intend to sow with a shade tolerant mix in a few weeks.I'd like to get a weak feed into the soil beforehand to cover that possibility.Is that totally a no no? I acted on a bit of advice last year without success and I'm running out of options. I don't think it's leatherjackets but I'll probably try nematodes later on.

My main question is what to feed/treat this ground with when it get's a bit drier,just to make sure there's something in there before I get around to sowing.

(I'll aerate first and usually mix seed wth 'John Innes'.)