[chryuop]

I have a question about a certain reading of certain kanji and I noticed mostly it happens with the Chinese reading.
There are kanji that amongst all their readings, they finish with つ, like for example 出　（しゅつ）、立　（りつ）、早　（さつ） ecc... In some of them the tsu is small (sorry didn't know how to write the small kana with the IME), while some of them it is regular tsu.
My question is what the pronunciations are? I mean are they strict like the dictionaries write them or the native speakers change them according on how they sound better to them?