I'm by no means an expert on the area, but I've experienced a similar problem with my own guitars, and there are a few thing I can recommend you try.

First off, is the room temperature stable or does it change greatly (f.ex. do you have open windows in the room)? This caused my guitars to go out of tune frequently, because the string length increases the warmer the room is, and decreases the colder the room is. This either increases or decreases the tension, leading to unstable tuning. Try making sure to close any windows or other entrances to your practice space about an hour before practicing (if possible, and only viable if you always practice at a certain time of the day). This gives the room time to temperate, even if you've just had all windows in the house open. And since the room has the right temperature every time you practice, your guitar won't have to be re-tuned every time, as long as you don't choose to change the practice-temperature.

Secondly, are there two or more complete windings around the tuning machines? If not, the tension from the strings can in some cases pull the string a bit looser so it goes out of tune. If there aren't 2 windings, you may want to re-syring your guitar and make sure there's the required number of windings.

Those were the two biggest issues I had when my guitars wouldn't stay tuned. Hope it helps a bit :)