Inbetween the 6.5 to 7.5 range should be good. Never want it too low or high. I would try giving it some of the nutes containing the mag for the brown and it has nitrogen and potassium for the yellow and purple ...If the ph isnt the problem. Does she get regular feedings? If not it coulda been using up and running out of whatever the soil had to offer. As for the lighting im n ot sure because i dont grow under any lights to flower. For such a huge plant it would seem that it could benefit more outside. Get that sunlight from all angles.