my seed compost looks and feels wrong - can someone help?

I must be old school still mix my own have tried mutipurpose not very pleased with it.
If I remember correct in my early training days (city and guilds) seed compost should have a lot less strength fertilizer , as too strong inhibits germination on a lot of seeds therefore if the seed germinates well in it there not enough for growing on plants. I cant see as there is a multipurpose compost. and you get what you pay for

 

I'm afraid my info is second hand (hence me saying I'd heard tales). I'm not sure where my sources got that info from. They said they'd seen it on the telly but either they were vague or I wasn't listening properly I'm afraid.