what’s up with my potted trees?

I have a couple of spruce including a blue spruce i only bought last year,also a holly only maybe two year old potted in decent pots. this year as we came in to spring we started loosing all the pines, the same on the holly. This has continued and the holly is almost leafless. I tried re-potting with a larger pot and good compost but to no avail. all the pine seem to go red before dropping.