Texting is a lot for you, but it's not objectively wrong - some people enjoy it.
If OP's friends used to text her daily with every sign of enthusiasm, it's not necessarily right to assume that they have always found this level of contact boring/annoying and been looking for a way to escape it....
OP, it may be that you have done something to upset them you aren't aware of, OR may simply be that their lives have moved on and they are focusing on other friendships. Your choices I suppose, are;
A) accept the new, reduced level of friendship and simply text occasionally/on special occasions.
B) stop texting altogether, if this is too hurtful/doesn't work for you.
C) ask them about it. This is a bit of a nuclear option as they may feel criticised/got at and cease the friendship, but if you are thinking of stopping contacting them anyway, perhaps you have nothing to lose. If you force a confrontation over something like this, tho, I guess you have to be prepared to hear potentially hurtful things.
I once called out two previously close friends who had stopped contacting me, because I believed they had listened to malicious gossip spread by another and I felt pretty furious that they had believed someone known to be a sensationalist and liar, over me. One of them ignored my message and I never heard from her again, the other sent a pretty crushing message basically saying she had priorities in her life and I wasn't one of them.
For this reason I wouldn't recommend this course of action unless you are feeling very emotionally robust!
Good luck, whatever you decide to do.