m0useanswered grow question 3 years ago BioBIzz light mix is comprised of Peat moss, Sphagnum peat and Perlite
add coir into that and its soilless not soil.
Using liquid nutes in soilless PH should be around 5.5-6.2 range.
Coir is also void of nutrients and if its not buffered it will rob your feed of calcium and magnesium.
I'd suggest adding in some calmg and following the feeding schedules of Sensi coco grow A and B.
all the ph fluxing could be causing some of what you are seeing right now.
Yellow from the inside out on new growth is also pointing towards signs of it needing Iron.
I'd also invest in a TDS pen. You should know your EC/PPM of your feeding solution and runoff.
Try some of these steps and see how it fares in the next week.