This is perfectly normal if u are counting 4 weeks from flip of lights. Some strains can take longer than 2 weeks to even start pistils and have been known to go 14-15 weeks in flower. Just happens sometimes.
I even just had a cheese auto take 6 weeks to start flower and flowering very slow. It will happen, patience sucks
I agree with @anon95385719 sounds like a non issue
Once they start you’ll be ok
But I would also like to know if they are autos or photos plants if autos and your lights are not on a 12-12 switch to 12-12 can help
How much light are you using ?