Leaves yellowing

I'm not entirely sure. But it looks like a deficiency. A nitrogen deficiency causes the older, lower leaves of the plant to turn yellow, wilt, and eventually die. The plant typically appears pale or light green. The yellow leaves of a nitrogen deficiency may show brown signs, and they usually become soft and "wrinkle" before they might become crispy, but eventually fall off by themselves. When the older lower leaves change, it's often a deficiency because the plant pulls the missing nutrients from the older leaves. The humidity is also a bit too high at 75%. Ideally, it should be between 50-60% RH during this stage and between 40-50% RH during flowering to avoid mold in the buds.