Hello
So try checking both in going and runoff ph. If you can do plain water to raise it good, but i think you're going to need some calcium added in. If you have a calmag supplement good, otherwise eggshells and epsom salt can be supplement, if you don't have and ph up or down drops or powder there are some natural ways, any sort of garden store lime products will raise ph as well as potassium carbonate , baking soda can help to raise the ph.
It's true that you don't usually have to adjust the ph as strictly with soil growing because of buffering capacity, but that mostly applies to living soil situations and is still worth being monitored occasionally.
*maybe check the ph of water that has just a calmag supplement, if its reasonably high 6.5-7 you can water that in plain and it will help raise the root zone, if your roots are very low, then even watering with up near 7.5 would probably be alright. Try a few things and keep checking and see what works best for you.
Happy growing. ✌️