4 year old mispronouncing many words/sounds?

[Itsjustmeagain]

My just turned 4 year old has many letters she just cant say so she mispronounces them everytime. TBH I thought she would grow out of it but she just isnt. Its things like saying S instead of F or d instead of "st".

At what age does this become an issue? she has good speech other than these issues (she will hold a conversation properly etc)

My DD is nearly 5 and has recently been discharged from speech and language as she has caught up with the lower end of normal range.
She still says 't' instead of 'c' and 'd' instead of 'g' and 'f' instead of 'sp' and almost totally unintelligible when upset/cross.
She has had one to one Speech therapy once a week for two years to get to this stage.

DS is nearly six and still can't say th or R properly, and mixes up syllables (ambliance, basgetti, uses "shouldn't of" to mean "should have")

I think it's normal. Is she starting school in Sept? I'm sure they'll pick up if it's an issue.

I knew my DS was pronouncing things wrong but he chatted away and we knew what he meant. But when he started preschool last sept at 3 years 9 months the teacher recommended a referral to speech and language. Took 3 months for an assessment. It was very interesting watching her point at pictures then write the sounds he was actually saying next the picture. He knew all the words but 3/4 weren't said right.

He didn't know how to say "f" or "s" at all, let alone use them in words properly.

So a month later we started weekly appointments for 4 weeks then a month off then another 4 weeks. 10mins a day at home practise as well. He is much much better but still not yet saying the correct sound all the time without prompting, although knows the word when prompted.

I just phoned my health visitor to get the initial referral. I had discussed it with her at a younger siblings appointment but she said it can just be immaturity but by 4 their speech should be coming more consistent so we were giving him till he was 4 before preschool recommended acting soon.