Nutes or PH issue?

What do you think is happening here? Grow specs are: Autopot, coco, 18/6, GH Flora with added Folvic and GP's Procal and Potassium Silicate, fed at 1100 Ppm and 6.0 PH. Lighting is Alibaba Quantum Board, turned up to 178.4 watts. Strains are Dimafem Critical Plus and Orange Juice photos. Ph dipped to 5.3 for a few hours - not sure if that could be the culprit.

Ya 5.3 ph was that ya run off or what's in ya tank ?
1100 ppm is massively strong ,
Are you sure it's 1100 ppm and not 1.1ec ? If ya going by ppm' ya want to be somewhere about 450 ppm and work upto 600 full flower , depending on strain ya can push that little bit further . Other than that they look good . It's new growth ya need to keep an eye on