The first one could possibly be cats ear or a similar Dandelion relative! Groundsel is usually a bit more upright and greener - you should be able to see the yellow flower heads appearing. Ragwort - also would be greener and starts off as a more compact shorter plant. If you can leave a bit longer it will soon be possible to tell, or else if you can post any photos from different angles it might help.
Did you buy a pack of yellow seeds?