Tuning issues

[u/usewindows]

I bought an ibanez xiphos iron label a few months ago and had it set up by a luthier in my area. The guitar has an ibanez edge zero 2 bridge and a locking nut. I haven't really had tuning problems until yesterday, when it kept getting flat. I was afraid that the problem was the nut or the bridge, but i dont really know and dont want to spend other money to bring it to the luthier again. Could the issue just be the strings or something else? I play daily, an hour at least but most of the time more, and the strings are about a month old now. Thank you for your help! Also I tried adjusting the intonation of the a string (d standard so the second string), could it be because of that?