Leaves Turning Crispy And Yellow

i have 2 swiss cheese plants and both are having this problem of starting from the lowest fan leaves and working its way up is some kind of virus or something i originally thought it was the pH balance but now even that is netural and the plant still is getting crispy leaves so im stumped they are in 2nd wk flowering so yellow not too worried about, but the crispy part is annoying the heck out of me, i have the plants in MG soil and using orzarka natural spring water, here is a picutre what is your diagnosis

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