Calling All Vets, Trichomes checking question

I have a Pandora's Box plant in the 8th week of flowering. The stuff I have read says the window of harvest is the 9th week. But, from what I have read on the forum results may vary.So, I have two questions. The first is in regards to checking the trichomes. Are there any signs you can see on the plant that let you know when it is time to check the trichomes? I would say at least 25 to 30% of the hairs are red now. Is that a sign?
Second question is about, yellowing spots on the leaves. I had this problem in the beginning (3rd week) and you guys helped me fix it (underfeeding). This week I am using this feeding schedule
0 floraGro
10 ml FloraMicro
20 ml FloraBloom
5 ml floralicious Bloom
10 ml liquid KloolBloom
3/4 teaspoon Bcuz Bloom (from Atami)
10 ml KalMag Plus
**per 1 Gallon Distilled Water
For the most part its the "GH Expert Recirculating Program" minus the Flora Blend and FloraNectar. And, plus the Bcuzz Bloom. My ppm level this morning was 1340. Does the yellowing of the leaves mean the plant is finishing. Or is it my nute recipe that is hurting her? I am a first timer so I have no idea. I remember reading on here that plants start to look bad when they are finishing up. The yellow spots and browning of lower leaves started about half way through the 7wk of flowering. I know its not my ph level, I check it every day and its consistent. Any help from the vets on the forum would be greatly appreciated.

I would say that your phosphorus are probably kind of high and from the yellowing you might have needed a little nitrogen. But you're close enough now to finish that I would just start water with straight water to start the flushing process.