Leaves dying on small auto

are you using tap water or bottled water? because tap water is always a bad idea as it's contaminated and will cause ph fluctuation.

this looks like it could be your ph is fluctuating or has never been checked and is off ph, try watering it at 6.2 to 6.5 ph, should do the trick. also nutrients can upset the ph value when mixing them up, if organic nutrients are used then almost always will result in a lower ph so i've found.