Took 2g glycine and had a terrible reaction. Any idea why?

I took 2g glycine a few nights ago and I slept well but woke up the next day feeling very depressed and emotionally numb, also with bad brain fog. A few days have passed and the depression has lifted a bit but I still feel quite low and have terrible brain fog. Trying to figure out what could have happened. I am on quite a high dose of an antidepressant (Nortriptyline) and currently tapering Olanzapine (last reduced months ago) so I’m wondering if maybe the combination of glycine and my meds could have caused this. Hoping it’s temporary.