yellow leaves and brown leaves

It looks ph related in substrate die to multiple issues starting at once.

No diary = no information. It's relatively impossible to tell you what you should do if all we're given is photos... We need the information that is contained in a diary! What are you growing, auto or photo? How old are they? What's the substrate? What's the pH? What are your nutes? How much nutes have you been giving them? What the temp? What's the humidity? How old are they? We WANT to help but we need information before we can do even a halfway decent job of advising you... Join the community and start a diary - even if you can only reconstruct the last week or two... And if you just put that information into a comment here, we're not going to even know you've done so unless we come back to look which rarely happens... Start a diary and pose your question again!