Help needed. Deficiency

How's it.
Iv been growing in autopots a few years now. The last 2 or 3 runs iv been running into a deficiency or some drama when I flip the plants to flower. Seems to kick in hard around the 2nd week of flower. I clone this lot to keep them going. I use 15 litre Single modules.
Run canna coco nutes with rizo and cannazyme at half strength, drip clean in res and CMX( calmag )at 1ml a litre. EC is 1.6 and PH is kept between 5.8 - 6.1.
Led lights. Res temp is about 16 degrees cold but it's a cold climate were I am. It's got worse this run to the point the plants have almost carked it or completely stopped stunted growth. Any help or advice would be greatly appreciated. Hope pics have uploaded.

Im a soil guy but the temp sticks out to me

I have 2 flower tents both same temps seperate res. I though at the start it could of been that but It's only been happening to one lot of plants. I'll get some better pics in a few hours. I clone to keep a few strains going an it's only affecting one lot. So it's got me stumped

Those pictures look like retaining water due to temperatures. Even if it’s just a single strain. Your temperature is far too low for optimal growth under LED. It looks like possible early magnesium deficiency as well but that could be shading.