I started a Bubblicious and a Lavender Kush seed soaking in water for 36 hours before planting to soil. The Bubblicious broke surface in two days and is now working on it’s third set of true leaves. The Lavender Kush took eight days to break surface and is just now starting it’s first true leaves.
Is this a strain related issue?
Been my experience that most kush strains tend to veg a little slower and seeds are always greatly varied even if same strain in how they sprout and grow never let a slow start fool you have had plants I thought were runts pick right up in flower and put their sisters to shame.
Every strain is different - that’s the fun of growing watching the plant produce those beautiful buds. Nothing is wrong - good to be concerned and all ways good to keep an eye out for plant issues. Happy Cultivation !!!
I agree with both Steve and Donald.
B Safe
Will
When seeds are stored and dormant for long periods of time; It takes longer to propagate. Might be as simple as that. 
I doing some bag seed right now and its going on day 6 and nothing yet.
Will
Here is a picture of the Bubblicious (BUB) ans the Lavender Kush on day 18 from start of germination.
Will, I am playing with bag seed also (CCS, CAPE COD STREET) Started (3) small plants and tossed them in 12/12 and picked of the male. Returned to veg and now (5) weeks into 12/12. Took clones which rooted fast and no sign of hemies. Looking good and sticky.
Not a bad looking little grow area there…TMC