My 2 year old started adding random consonant sounds at the end of words...something to be concerned about?

I was told not to really worry about speech issues unless they are a problem after 4. My youngest 3 all had/have strange speech problems with certain letters and words. My older one has no issues any more for over a year now. My youngest 2 at home both can't say their s's well, or k sounds well among other letters. They also add consanants at the end of words- pants are pant-eds. Don't stress too much, they are learning language still and trying to figure it all out.